diff --git a/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button-debug.js b/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button-debug.js
index f20942dbce1..86270a2d495 100644
--- a/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button-debug.js
+++ b/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button-debug.js
@@ -92,7 +92,10 @@ var CSS = {
             margin: '0 0 0 0.5em'
         }
     ],
-
+    DEFAULTS = {
+        WIDTH: 160,
+        HEIGHT: 160,
+    },
     REGEX = {
         ISPERCENT: /\d+%/
     },
@@ -550,22 +553,23 @@ Y.namespace('M.atto_image').Button = Y.Base.create('button', Y.M.editor_atto.Edi
         image.onload = function() {
             var input, currentwidth, currentheight, widthRatio, heightRatio;
 
+            // Store dimensions of the raw image, falling back to defaults for images without dimensions (e.g. SVG).
             self._rawImageDimensions = {
-                width: this.width,
-                height: this.height
+                width: this.width || DEFAULTS.WIDTH,
+                height: this.height || DEFAULTS.HEIGHT,
             };
 
             input = self._form.one('.' + CSS.INPUTWIDTH);
             currentwidth = input.get('value');
             if (currentwidth === '') {
-                input.set('value', this.width);
-                currentwidth = "" + this.width;
+                input.set('value', self._rawImageDimensions.width);
+                currentwidth = "" + self._rawImageDimensions.width;
             }
             input = self._form.one('.' + CSS.INPUTHEIGHT);
             currentheight = input.get('value');
             if (currentheight === '') {
-                input.set('value', this.height);
-                currentheight = "" + this.height;
+                input.set('value', self._rawImageDimensions.height);
+                currentheight = "" + self._rawImageDimensions.height;
             }
             input = self._form.one('.' + CSS.IMAGEPREVIEW);
             input.setAttribute('src', this.src);
@@ -576,13 +580,10 @@ Y.namespace('M.atto_image').Button = Y.Base.create('button', Y.M.editor_atto.Edi
             input = self._form.one('.' + CSS.INPUTCONSTRAIN);
             if (currentwidth.match(REGEX.ISPERCENT) && currentheight.match(REGEX.ISPERCENT)) {
                 input.set('checked', currentwidth === currentheight);
+            } else if (this.width === 0 || this.height === 0) {
+                // If we don't have both dimensions of the image, we can't auto-size it, so disable control.
+                input.set('disabled', 'disabled');
             } else {
-                if (this.width === 0) {
-                    this.width = 1;
-                }
-                if (this.height === 0) {
-                    this.height = 1;
-                }
                 // This is the same as comparing to 3 decimal places.
                 widthRatio = Math.round(1000 * parseInt(currentwidth, 10) / this.width);
                 heightRatio = Math.round(1000 * parseInt(currentheight, 10) / this.height);
diff --git a/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button-min.js b/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button-min.js
index 9a9522be60f..a3203a060b7 100644
--- a/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button-min.js
+++ b/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button-min.js
@@ -1,3 +1,3 @@
-YUI.add("moodle-atto_image-button",function(c,e){var u={RESPONSIVE:"img-fluid",INPUTALIGNMENT:"atto_image_alignment",INPUTALT:"atto_image_altentry",INPUTHEIGHT:"atto_image_heightentry",INPUTSUBMIT:"atto_image_urlentrysubmit",INPUTURL:"atto_image_urlentry",INPUTSIZE:"atto_image_size",INPUTWIDTH:"atto_image_widthentry",IMAGEALTWARNING:"atto_image_altwarning",IMAGEURLWARNING:"atto_image_urlwarning",IMAGEBROWSER:"openimagebrowser",IMAGEPRESENTATION:"atto_image_presentation",INPUTCONSTRAIN:"atto_image_constrain",INPUTCUSTOMSTYLE:"atto_image_customstyle",IMAGEPREVIEW:"atto_image_preview",IMAGEPREVIEWBOX:"atto_image_preview_box",ALIGNSETTINGS:"atto_image_button"},n={URL:"urlentry",ALT:"altentry"},t={INPUTURL:"."+u.INPUTURL},s=[{name:"verticalAlign",str:"alignment_top",value:"text-top",margin:"0 0.5em"},{name:"verticalAlign",str:"alignment_middle",value:"middle",margin:"0 0.5em"},{name:"verticalAlign",str:"alignment_bottom",value:"text-bottom",margin:"0 0.5em",isDefault:!0},{name:"float",str:"alignment_left",value:"left",margin:"0 0.5em 0 0"},{name:"float",str:"alignment_right",value:"right",margin:"0 0 0 0.5em"}],I=/\d+%/,_="atto_image",p='<img src="{{url}}" alt="{{alt}}" {{#if width}}width="{{width}}" {{/if}}{{#if height}}height="{{height}}" {{/if}}{{#if presentation}}role="presentation" {{/if}}{{#if customstyle}}style="{{customstyle}}" {{/if}}{{#if classlist}}class="{{classlist}}" {{/if}}{{#if id}}id="{{id}}" {{/if}}/>';c.namespace("M.atto_image").Button=c.Base.create("button",c.M.editor_atto.EditorPlugin,[],{_currentSelection:null,_selectedImage:null,_form:null,_rawImageDimensions:null,initializer:function(){this.addButton({icon:"e/insert_edit_image",callback:this._displayDialogue,tags:"img",tagMatchRequiresAll:!1}),this.editor.delegate("dblclick",this._displayDialogue,"img",this),this.editor.delegate("click",this._handleClick,"img",this),this.editor.on("paste",this._handlePaste,this),this.editor.on("drop",this._handleDragDrop,this),this.editor.on("dragover",function(e){e.preventDefault()},this),this.editor.on("dragenter",function(e){e.preventDefault()},this)},_handleDragDrop:function(e){return!e._event||!e._event.dataTransfer||this._handlePasteOrDropHelper(e,e._event.dataTransfer)},_handlePaste:function(e){return!e._event||!e._event.clipboardData||this._handlePasteOrDropHelper(e,e._event.clipboardData)},_handlePasteOrDropHelper:function(e,t){var i,n,a=t.items,s=!1;for(i=0;i<a.length;i++)"file"===(n=a[i]).kind&&this._isImage(n.type)&&(this._uploadImage(n.getAsFile()),s=!0);return!s||(e.preventDefault(),e.stopPropagation(),!1)},_isImage:function(e){return 0===e.indexOf("image/")},_uploadImage:function(e){var t,i,n,a,s,o,l,r,h,g=this,d=this.get("host"),m=c.Handlebars.compile(p);for(d.saveSelection(),require(["core_form/events"],function(e){e.notifyUploadStarted(g.editor.get("id"))}),i=(t=d.get("filepickeroptions").image).savepath===undefined?"/":t.savepath,n=new FormData,a=0,s="",o=new XMLHttpRequest,l="",r=Object.keys(t.repositories),n.append("repo_upload_file",e),n.append("itemid",t.itemid),h=0;h<r.length;h++)if("upload"===t.repositories[r[h]].type){n.append("repo_id",t.repositories[r[h]].id);break}n.append("env",t.env),n.append("sesskey",M.cfg.sesskey),n.append("client_id",t.client_id),n.append("savepath",i),n.append("ctx_id",t.context.id),a=(new Date).getTime(),s="moodleimage_"+Math.round(1e5*Math.random())+"-"+a,d.focus(),d.restoreSelection(),l=m({url:M.util.image_url("i/loading_small","moodle"),alt:M.util.get_string("uploading",_),id:s}),d.insertContentAtFocusPoint(l),g.markUpdated(),o.onreadystatechange=function(){var e,t,i,n,a=g.editor.one("#"+s);if(4===o.readyState){if(200===o.status){if(e=JSON.parse(o.responseText)){if(e.error)throw a&&a.remove(!0),require(["core_form/events"],function(e){e.notifyUploadCompleted(g.editor.get("id"))}),new M.core.ajaxException(e);(t=e).event&&"fileexists"===e.event&&(t=e.newfile),i=m({url:t.url,presentation:!0,classlist:u.RESPONSIVE}),n=c.Node.create(i),a?a.replace(n):g.editor.appendChild(n),g.markUpdated()}}else c.use("moodle-core-notification-alert",function(){require(["core_form/events"],function(e){e.notifyUploadCompleted(g.editor.get("id"))}),new M.core.alert({message:M.util.get_string("servererror","moodle")})}),a&&a.remove(!0);require(["core_form/events"],function(e){e.notifyUploadCompleted(g.editor.get("id"))})}},o.open("POST",M.cfg.wwwroot+"/repository/repository_ajax.php?action=upload",!0),o.send(n)},_handleClick:function(e){var t=e.target,i=this.get("host").getSelectionFromNode(t);this.get("host").getSelection()!==i&&this.get("host").setSelection(i)},_displayDialogue:function(){if(this._currentSelection=this.get("host").getSelection(),!1!==this._currentSelection){this._rawImageDimensions=null;var e=this.getDialogue({headerContent:M.util.get_string("imageproperties",_),width:"auto",focusAfterHide:!0,focusOnShowSelector:t.INPUTURL});e.get("boundingBox").setStyle("maxWidth","90%"),e.set("bodyContent",this._getDialogueContent()).show()}},_loadPreviewImage:function(e){var t=new Image,s=this;t.onerror=function(){s._form.one("."+u.IMAGEPREVIEW).setStyles({display:"none"}),s.getDialogue().centerDialogue()},t.onload=function(){var e,t,i,n,a;s._rawImageDimensions={width:this.width,height:this.height},""===(t=(e=s._form.one("."+u.INPUTWIDTH)).get("value"))&&(e.set("value",this.width),t=""+this.width),""===(i=(e=s._form.one("."+u.INPUTHEIGHT)).get("value"))&&(e.set("value",this.height),i=""+this.height),(e=s._form.one("."+u.IMAGEPREVIEW)).setAttribute("src",this.src),e.setStyles({display:"inline"}),e=s._form.one("."+u.INPUTCONSTRAIN),t.match(I)&&i.match(I)?e.set("checked",t===i):(0===this.width&&(this.width=1),0===this.height&&(this.height=1),n=Math.round(1e3*parseInt(t,10)/this.width),a=Math.round(1e3*parseInt(i,10)/this.height),e.set("checked",n===a)),s._autoAdjustSize(s),s.getDialogue().centerDialogue()},t.src=e},_getDialogueContent:function(){var e=c.Handlebars.compile(
-'<form class="atto_form"><div style="display:none" role="alert" class="alert alert-warning mb-1 {{CSS.IMAGEURLWARNING}}"><label for="{{elementid}}_{{CSS.INPUTURL}}">{{get_string "imageurlrequired" component}}</label></div>{{#if showFilepicker}}<div class="mb-1"><label for="{{elementid}}_{{CSS.INPUTURL}}">{{get_string "enterurl" component}}</label><div class="input-group input-append w-100"><input name="{{FORMNAMES.URL}}" class="form-control {{CSS.INPUTURL}}" type="url" id="{{elementid}}_{{CSS.INPUTURL}}" size="32"/><span class="input-group-append"><button class="btn btn-secondary {{CSS.IMAGEBROWSER}}" type="button">{{get_string "browserepositories" component}}</button></span></div></div>{{else}}<div class="mb-1"><label for="{{elementid}}_{{CSS.INPUTURL}}">{{get_string "enterurl" component}}</label><input name="{{FORMNAMES.URL}}" class="form-control fullwidth {{CSS.INPUTURL}}" type="url" id="{{elementid}}_{{CSS.INPUTURL}}" size="32"/></div>{{/if}}<div style="display:none" role="alert" class="alert alert-warning mb-1 {{CSS.IMAGEALTWARNING}}"><label for="{{elementid}}_{{CSS.INPUTALT}}">{{get_string "presentationoraltrequired" component}}</label></div><div class="mb-1"><label for="{{elementid}}_{{CSS.INPUTALT}}">{{get_string "enteralt" component}}</label><textarea class="form-control fullwidth {{CSS.INPUTALT}}" id="{{elementid}}_{{CSS.INPUTALT}}" name="{{FORMNAMES.ALT}}" maxlength="125"></textarea><div id="the-count" class="d-flex justify-content-end small"><span id="currentcount">0</span><span id="maximumcount"> / 125</span></div><div class="form-check"><input type="checkbox" class="form-check-input {{CSS.IMAGEPRESENTATION}}" id="{{elementid}}_{{CSS.IMAGEPRESENTATION}}"/><label class="form-check-label" for="{{elementid}}_{{CSS.IMAGEPRESENTATION}}">{{get_string "presentation" component}}</label></div></div><div class="mb-1"><label class="" for="{{elementid}}_{{CSS.INPUTSIZE}}">{{get_string "size" component}}</label><div id="{{elementid}}_{{CSS.INPUTSIZE}}" class="form-inline {{CSS.INPUTSIZE}}"><label class="accesshide" for="{{elementid}}_{{CSS.INPUTWIDTH}}">{{get_string "width" component}}</label><input type="text" class="form-control mr-1 input-mini {{CSS.INPUTWIDTH}}" id="{{elementid}}_{{CSS.INPUTWIDTH}}" size="4"/> x<label class="accesshide" for="{{elementid}}_{{CSS.INPUTHEIGHT}}">{{get_string "height" component}}</label><input type="text" class="form-control ml-1 input-mini {{CSS.INPUTHEIGHT}}" id="{{elementid}}_{{CSS.INPUTHEIGHT}}" size="4"/><div class="form-check ml-2"><input type="checkbox" class="form-check-input {{CSS.INPUTCONSTRAIN}}" id="{{elementid}}_{{CSS.INPUTCONSTRAIN}}"/><label class="form-check-label" for="{{elementid}}_{{CSS.INPUTCONSTRAIN}}">{{get_string "constrain" component}}</label></div></div></div><div class="form-inline mb-1"><label class="for="{{elementid}}_{{CSS.INPUTALIGNMENT}}">{{get_string "alignment" component}}</label><select class="custom-select {{CSS.INPUTALIGNMENT}}" id="{{elementid}}_{{CSS.INPUTALIGNMENT}}">{{#each alignments}}<option value="{{value}}">{{get_string str ../component}}</option>{{/each}}</select></div><input type="hidden" class="{{CSS.INPUTCUSTOMSTYLE}}"/><br/><div class="mdl-align"><div class="{{CSS.IMAGEPREVIEWBOX}}"><img class="{{CSS.IMAGEPREVIEW}}" alt="" style="display: none;"/></div><button class="btn btn-secondary {{CSS.INPUTSUBMIT}}" type="submit">{{get_string "saveimage" component}}</button></div></form>'),t=this.get("host").canShowFilepicker("image"),i=c.Node.create(e({elementid:this.get("host").get("elementid"),CSS:u,FORMNAMES:n,component:_,showFilepicker:t,alignments:s}));return this._form=i,this._applyImageProperties(this._form),this._form.one("."+u.INPUTURL).on("blur",this._urlChanged,this),this._form.one("."+u.INPUTURL).on("change",this._hasErrorUrlField,this),this._form.one("."+u.IMAGEPRESENTATION).on("change",this._hasErrorAltField,this),this._form.one("."+u.INPUTALT).on("blur",this._hasErrorAltField,this),this._form.one("."+u.INPUTWIDTH).on("blur",this._autoAdjustSize,this),this._form.one("."+u.INPUTHEIGHT).on("blur",this._autoAdjustSize,this,!0),this._form.one("."+u.INPUTCONSTRAIN).on("change",function(e){e.target.get("checked")&&this._autoAdjustSize(e)},this),this._form.one("."+u.INPUTSUBMIT).on("click",this._setImage,this),t&&this._form.one("."+u.IMAGEBROWSER).on("click",function(){this.get("host").showFilepicker("image",this._filepickerCallback,this)},this),this._form.one("."+u.INPUTALT).on("keyup",this._handleKeyup,this),i},_autoAdjustSize:function(e,t){var i,n,a,s,o,l,r,h,g,d,m;t=t||!1,i=this._form.one("."+u.INPUTWIDTH),n="width",a=this._form.one("."+u.INPUTHEIGHT),s="height",o=this._form.one("."+u.INPUTCONSTRAIN),l=i.get("value"),r=a.get("value"),h=this._form.one("."+u.IMAGEPREVIEW),this._rawImageDimensions&&(""===l&&(l=this._rawImageDimensions[n],i.set("value",l),l=i.get("value")),h.setStyles({width:null,height:null}),o.get("checked")?(t&&(m=i,i=a,a=m,m=n,n=s,s=m,m=l,l=r,r=m),l.match(I)?(r=l,g=parseInt(l,10),d=this._rawImageDimensions.width/100*g,h.setStyle("width",d),d=this._rawImageDimensions.height/100*g,h.setStyle("height",d)):(r=Math.round(l/this._rawImageDimensions[n]*this._rawImageDimensions[s]),t?h.setStyles({width:r,height:l}):h.setStyles({width:l,height:r})),a.set("value",r)):(l.match(I)?(g=parseInt(l,10),d=this._rawImageDimensions.width/100*g,h.setStyle("width",d+"px")):h.setStyle("width",l+"px"),r.match(I)?(g=parseInt(r,10),d=this._rawImageDimensions.height/100*g,h.setStyle("height",d+"px")):h.setStyle("height",r+"px")))},_filepickerCallback:function(e){""!==e.url&&(this._form.one("."+u.INPUTURL).set("value",e.url),this._form.one("."+u.INPUTWIDTH).set("value",""),this._form.one("."+u.INPUTHEIGHT).set("value",""),this._loadPreviewImage(e.url))},_applyImageProperties:function(t){var e=this._getSelectedImageProperties(),i=t.one("."+u.IMAGEPREVIEW);if(!1===e)return i.setStyle("display","none"),void s.some(function(e){return!!e.isDefault&&(t.one("."+u.INPUTALIGNMENT).set("value",e.value),!0)},this)
-;e.align&&t.one("."+u.INPUTALIGNMENT).set("value",e.align),e.customstyle&&t.one("."+u.INPUTCUSTOMSTYLE).set("value",e.customstyle),e.width&&t.one("."+u.INPUTWIDTH).set("value",e.width),e.height&&t.one("."+u.INPUTHEIGHT).set("value",e.height),e.alt&&t.one("."+u.INPUTALT).set("value",e.alt),e.src&&(t.one("."+u.INPUTURL).set("value",e.src),this._loadPreviewImage(e.src)),e.presentation&&t.one("."+u.IMAGEPRESENTATION).set("checked","checked"),this._autoAdjustSize()},_getSelectedImageProperties:function(){var e,t,i,n,a={src:null,alt:null,width:null,height:null,align:"",presentation:!1},s=this.get("host").getSelectedNodes();return(s=s&&s.filter("img"))&&s.size()?(n=this._removeLegacyAlignment(s.item(0)),i=(this._selectedImage=n).getAttribute("style"),a.customstyle=i,(e=n.getAttribute("width")).match(I)||(e=parseInt(e,10)),(t=n.getAttribute("height")).match(I)||(t=parseInt(t,10)),0!==e&&(a.width=e),0!==t&&(a.height=t),this._getAlignmentPropeties(n,a),a.src=n.getAttribute("src"),a.alt=n.getAttribute("alt")||"",a.presentation="presentation"===n.get("role"),a):(this._selectedImage=null,!1)},_getAlignmentPropeties:function(i,n){var a;!s.some(function(e){var t=this._getAlignmentClass(e.value);return i.hasClass(t)?(n.align=e.value,!0):(e.isDefault&&(a=e.value),!1)},this)&&a&&(n.align=a)},_urlChanged:function(){var e=this._form.one("."+u.INPUTURL);""!==e.get("value")&&this._loadPreviewImage(e.get("value"))},_setImage:function(e){var t,i=this._form,n=i.one("."+u.INPUTURL).get("value"),a=i.one("."+u.INPUTALT).get("value"),s=i.one("."+u.INPUTWIDTH).get("value"),o=i.one("."+u.INPUTHEIGHT).get("value"),l=this._getAlignmentClass(i.one("."+u.INPUTALIGNMENT).get("value")),r=i.one("."+u.IMAGEPRESENTATION).get("checked"),h=i.one("."+u.INPUTCONSTRAIN).get("checked"),g=i.one("."+u.INPUTCUSTOMSTYLE).get("value"),d=[],m=this.get("host");if(e.preventDefault(),!this._updateWarning()){if(m.focus(),""!==n){if(this._selectedImage?m.setSelection(m.getSelectionFromNode(this._selectedImage)):m.setSelection(this._currentSelection),h&&d.push(u.RESPONSIVE),d.push(l),!s.match(I)&&isNaN(parseInt(s,10)))return void i.one("."+u.INPUTWIDTH).focus();if(!o.match(I)&&isNaN(parseInt(o,10)))return void i.one("."+u.INPUTHEIGHT).focus();t=c.Handlebars.compile(p)({url:n,alt:a,width:s,height:o,presentation:r,customstyle:g,classlist:d.join(" ")}),this.get("host").insertContentAtFocusPoint(t),this.markUpdated()}this.getDialogue({focusAfterHide:null}).hide()}},_removeLegacyAlignment:function(i){return i.getStyle("margin")&&s.some(function(e){if(i.getStyle(e.name)!==e.value)return!1;var t=c.Node.create("<div>");return t.setStyle("margin",e.margin),i.getStyle("margin")===t.getStyle("margin")&&(i.addClass(this._getAlignmentClass(e.value)),i.setStyle(e.name,null),i.setStyle("margin",null),!0)},this),i},_getAlignmentClass:function(e){return u.ALIGNSETTINGS+"_"+e},_toggleVisibility:function(e,t){var i=this._form,n=i.all(e);n.setStyle("display",t?"block":"none")},_toggleAriaInvalid:function(e,t){var i=this._form;e.forEach(function(e){i.all(e).setAttribute("aria-invalid",t)})},_hasErrorUrlField:function(){var e=this._form,t=e.one("."+u.INPUTURL).get("value"),i=""===t;return this._toggleVisibility("."+u.IMAGEURLWARNING,i),this._toggleAriaInvalid(["."+u.INPUTURL],i),i},_hasErrorAltField:function(){var e=this._form,t=e.one("."+u.INPUTALT).get("value"),i=e.one("."+u.IMAGEPRESENTATION).get("checked"),n=""===t&&!i;return this._toggleVisibility("."+u.IMAGEALTWARNING,n),this._toggleAriaInvalid(["."+u.INPUTALT,"."+u.IMAGEPRESENTATION],n),n},_updateWarning:function(){var e=this._hasErrorUrlField(),t=this._hasErrorAltField(),i=e||t;return this.getDialogue().centerDialogue(),i},_handleKeyup:function(){var e=this._form,t=e.one("."+u.INPUTALT).get("value").length;e.one("#currentcount").setHTML(t)}})},"@VERSION@",{requires:["moodle-editor_atto-plugin"]});
\ No newline at end of file
+YUI.add("moodle-atto_image-button",function(c,e){var u={RESPONSIVE:"img-fluid",INPUTALIGNMENT:"atto_image_alignment",INPUTALT:"atto_image_altentry",INPUTHEIGHT:"atto_image_heightentry",INPUTSUBMIT:"atto_image_urlentrysubmit",INPUTURL:"atto_image_urlentry",INPUTSIZE:"atto_image_size",INPUTWIDTH:"atto_image_widthentry",IMAGEALTWARNING:"atto_image_altwarning",IMAGEURLWARNING:"atto_image_urlwarning",IMAGEBROWSER:"openimagebrowser",IMAGEPRESENTATION:"atto_image_presentation",INPUTCONSTRAIN:"atto_image_constrain",INPUTCUSTOMSTYLE:"atto_image_customstyle",IMAGEPREVIEW:"atto_image_preview",IMAGEPREVIEWBOX:"atto_image_preview_box",ALIGNSETTINGS:"atto_image_button"},n={URL:"urlentry",ALT:"altentry"},t={INPUTURL:"."+u.INPUTURL},s=[{name:"verticalAlign",str:"alignment_top",value:"text-top",margin:"0 0.5em"},{name:"verticalAlign",str:"alignment_middle",value:"middle",margin:"0 0.5em"},{name:"verticalAlign",str:"alignment_bottom",value:"text-bottom",margin:"0 0.5em",isDefault:!0},{name:"float",str:"alignment_left",value:"left",margin:"0 0.5em 0 0"},{name:"float",str:"alignment_right",value:"right",margin:"0 0 0 0.5em"}],o=160,l=160,I=/\d+%/,_="atto_image",p='<img src="{{url}}" alt="{{alt}}" {{#if width}}width="{{width}}" {{/if}}{{#if height}}height="{{height}}" {{/if}}{{#if presentation}}role="presentation" {{/if}}{{#if customstyle}}style="{{customstyle}}" {{/if}}{{#if classlist}}class="{{classlist}}" {{/if}}{{#if id}}id="{{id}}" {{/if}}/>';c.namespace("M.atto_image").Button=c.Base.create("button",c.M.editor_atto.EditorPlugin,[],{_currentSelection:null,_selectedImage:null,_form:null,_rawImageDimensions:null,initializer:function(){this.addButton({icon:"e/insert_edit_image",callback:this._displayDialogue,tags:"img",tagMatchRequiresAll:!1}),this.editor.delegate("dblclick",this._displayDialogue,"img",this),this.editor.delegate("click",this._handleClick,"img",this),this.editor.on("paste",this._handlePaste,this),this.editor.on("drop",this._handleDragDrop,this),this.editor.on("dragover",function(e){e.preventDefault()},this),this.editor.on("dragenter",function(e){e.preventDefault()},this)},_handleDragDrop:function(e){return!e._event||!e._event.dataTransfer||this._handlePasteOrDropHelper(e,e._event.dataTransfer)},_handlePaste:function(e){return!e._event||!e._event.clipboardData||this._handlePasteOrDropHelper(e,e._event.clipboardData)},_handlePasteOrDropHelper:function(e,t){var i,n,a=t.items,s=!1;for(i=0;i<a.length;i++)"file"===(n=a[i]).kind&&this._isImage(n.type)&&(this._uploadImage(n.getAsFile()),s=!0);return!s||(e.preventDefault(),e.stopPropagation(),!1)},_isImage:function(e){return 0===e.indexOf("image/")},_uploadImage:function(e){var t,i,n,a,s,o,l,r,h,g=this,d=this.get("host"),m=c.Handlebars.compile(p);for(d.saveSelection(),require(["core_form/events"],function(e){e.notifyUploadStarted(g.editor.get("id"))}),i=(t=d.get("filepickeroptions").image).savepath===undefined?"/":t.savepath,n=new FormData,a=0,s="",o=new XMLHttpRequest,l="",r=Object.keys(t.repositories),n.append("repo_upload_file",e),n.append("itemid",t.itemid),h=0;h<r.length;h++)if("upload"===t.repositories[r[h]].type){n.append("repo_id",t.repositories[r[h]].id);break}n.append("env",t.env),n.append("sesskey",M.cfg.sesskey),n.append("client_id",t.client_id),n.append("savepath",i),n.append("ctx_id",t.context.id),a=(new Date).getTime(),s="moodleimage_"+Math.round(1e5*Math.random())+"-"+a,d.focus(),d.restoreSelection(),l=m({url:M.util.image_url("i/loading_small","moodle"),alt:M.util.get_string("uploading",_),id:s}),d.insertContentAtFocusPoint(l),g.markUpdated(),o.onreadystatechange=function(){var e,t,i,n,a=g.editor.one("#"+s);if(4===o.readyState){if(200===o.status){if(e=JSON.parse(o.responseText)){if(e.error)throw a&&a.remove(!0),require(["core_form/events"],function(e){e.notifyUploadCompleted(g.editor.get("id"))}),new M.core.ajaxException(e);(t=e).event&&"fileexists"===e.event&&(t=e.newfile),i=m({url:t.url,presentation:!0,classlist:u.RESPONSIVE}),n=c.Node.create(i),a?a.replace(n):g.editor.appendChild(n),g.markUpdated()}}else c.use("moodle-core-notification-alert",function(){require(["core_form/events"],function(e){e.notifyUploadCompleted(g.editor.get("id"))}),new M.core.alert({message:M.util.get_string("servererror","moodle")})}),a&&a.remove(!0);require(["core_form/events"],function(e){e.notifyUploadCompleted(g.editor.get("id"))})}},o.open("POST",M.cfg.wwwroot+"/repository/repository_ajax.php?action=upload",!0),o.send(n)},_handleClick:function(e){var t=e.target,i=this.get("host").getSelectionFromNode(t);this.get("host").getSelection()!==i&&this.get("host").setSelection(i)},_displayDialogue:function(){if(this._currentSelection=this.get("host").getSelection(),!1!==this._currentSelection){this._rawImageDimensions=null;var e=this.getDialogue({headerContent:M.util.get_string("imageproperties",_),width:"auto",focusAfterHide:!0,focusOnShowSelector:t.INPUTURL});e.get("boundingBox").setStyle("maxWidth","90%"),e.set("bodyContent",this._getDialogueContent()).show()}},_loadPreviewImage:function(e){var t=new Image,s=this;t.onerror=function(){s._form.one("."+u.IMAGEPREVIEW).setStyles({display:"none"}),s.getDialogue().centerDialogue()},t.onload=function(){var e,t,i,n,a;s._rawImageDimensions={width:this.width||o,height:this.height||l},""===(t=(e=s._form.one("."+u.INPUTWIDTH)).get("value"))&&(e.set("value",s._rawImageDimensions.width),t=""+s._rawImageDimensions.width),""===(i=(e=s._form.one("."+u.INPUTHEIGHT)).get("value"))&&(e.set("value",s._rawImageDimensions.height),i=""+s._rawImageDimensions.height),(e=s._form.one("."+u.IMAGEPREVIEW)).setAttribute("src",this.src),e.setStyles({display:"inline"}),e=s._form.one("."+u.INPUTCONSTRAIN),t.match(I)&&i.match(I)?e.set("checked",t===i):0===this.width||0===this.height?e.set("disabled","disabled"):(n=Math.round(1e3*parseInt(t,10)/this.width),a=Math.round(1e3*parseInt(i,10)/this.height),e.set("checked",n===a)),s._autoAdjustSize(s),s.getDialogue().centerDialogue()},t.src=e},_getDialogueContent:function(){
+var e=c.Handlebars.compile('<form class="atto_form"><div style="display:none" role="alert" class="alert alert-warning mb-1 {{CSS.IMAGEURLWARNING}}"><label for="{{elementid}}_{{CSS.INPUTURL}}">{{get_string "imageurlrequired" component}}</label></div>{{#if showFilepicker}}<div class="mb-1"><label for="{{elementid}}_{{CSS.INPUTURL}}">{{get_string "enterurl" component}}</label><div class="input-group input-append w-100"><input name="{{FORMNAMES.URL}}" class="form-control {{CSS.INPUTURL}}" type="url" id="{{elementid}}_{{CSS.INPUTURL}}" size="32"/><span class="input-group-append"><button class="btn btn-secondary {{CSS.IMAGEBROWSER}}" type="button">{{get_string "browserepositories" component}}</button></span></div></div>{{else}}<div class="mb-1"><label for="{{elementid}}_{{CSS.INPUTURL}}">{{get_string "enterurl" component}}</label><input name="{{FORMNAMES.URL}}" class="form-control fullwidth {{CSS.INPUTURL}}" type="url" id="{{elementid}}_{{CSS.INPUTURL}}" size="32"/></div>{{/if}}<div style="display:none" role="alert" class="alert alert-warning mb-1 {{CSS.IMAGEALTWARNING}}"><label for="{{elementid}}_{{CSS.INPUTALT}}">{{get_string "presentationoraltrequired" component}}</label></div><div class="mb-1"><label for="{{elementid}}_{{CSS.INPUTALT}}">{{get_string "enteralt" component}}</label><textarea class="form-control fullwidth {{CSS.INPUTALT}}" id="{{elementid}}_{{CSS.INPUTALT}}" name="{{FORMNAMES.ALT}}" maxlength="125"></textarea><div id="the-count" class="d-flex justify-content-end small"><span id="currentcount">0</span><span id="maximumcount"> / 125</span></div><div class="form-check"><input type="checkbox" class="form-check-input {{CSS.IMAGEPRESENTATION}}" id="{{elementid}}_{{CSS.IMAGEPRESENTATION}}"/><label class="form-check-label" for="{{elementid}}_{{CSS.IMAGEPRESENTATION}}">{{get_string "presentation" component}}</label></div></div><div class="mb-1"><label class="" for="{{elementid}}_{{CSS.INPUTSIZE}}">{{get_string "size" component}}</label><div id="{{elementid}}_{{CSS.INPUTSIZE}}" class="form-inline {{CSS.INPUTSIZE}}"><label class="accesshide" for="{{elementid}}_{{CSS.INPUTWIDTH}}">{{get_string "width" component}}</label><input type="text" class="form-control mr-1 input-mini {{CSS.INPUTWIDTH}}" id="{{elementid}}_{{CSS.INPUTWIDTH}}" size="4"/> x<label class="accesshide" for="{{elementid}}_{{CSS.INPUTHEIGHT}}">{{get_string "height" component}}</label><input type="text" class="form-control ml-1 input-mini {{CSS.INPUTHEIGHT}}" id="{{elementid}}_{{CSS.INPUTHEIGHT}}" size="4"/><div class="form-check ml-2"><input type="checkbox" class="form-check-input {{CSS.INPUTCONSTRAIN}}" id="{{elementid}}_{{CSS.INPUTCONSTRAIN}}"/><label class="form-check-label" for="{{elementid}}_{{CSS.INPUTCONSTRAIN}}">{{get_string "constrain" component}}</label></div></div></div><div class="form-inline mb-1"><label class="for="{{elementid}}_{{CSS.INPUTALIGNMENT}}">{{get_string "alignment" component}}</label><select class="custom-select {{CSS.INPUTALIGNMENT}}" id="{{elementid}}_{{CSS.INPUTALIGNMENT}}">{{#each alignments}}<option value="{{value}}">{{get_string str ../component}}</option>{{/each}}</select></div><input type="hidden" class="{{CSS.INPUTCUSTOMSTYLE}}"/><br/><div class="mdl-align"><div class="{{CSS.IMAGEPREVIEWBOX}}"><img class="{{CSS.IMAGEPREVIEW}}" alt="" style="display: none;"/></div><button class="btn btn-secondary {{CSS.INPUTSUBMIT}}" type="submit">{{get_string "saveimage" component}}</button></div></form>'),t=this.get("host").canShowFilepicker("image"),i=c.Node.create(e({elementid:this.get("host").get("elementid"),CSS:u,FORMNAMES:n,component:_,showFilepicker:t,alignments:s}));return this._form=i,this._applyImageProperties(this._form),this._form.one("."+u.INPUTURL).on("blur",this._urlChanged,this),this._form.one("."+u.INPUTURL).on("change",this._hasErrorUrlField,this),this._form.one("."+u.IMAGEPRESENTATION).on("change",this._hasErrorAltField,this),this._form.one("."+u.INPUTALT).on("blur",this._hasErrorAltField,this),this._form.one("."+u.INPUTWIDTH).on("blur",this._autoAdjustSize,this),this._form.one("."+u.INPUTHEIGHT).on("blur",this._autoAdjustSize,this,!0),this._form.one("."+u.INPUTCONSTRAIN).on("change",function(e){e.target.get("checked")&&this._autoAdjustSize(e)},this),this._form.one("."+u.INPUTSUBMIT).on("click",this._setImage,this),t&&this._form.one("."+u.IMAGEBROWSER).on("click",function(){this.get("host").showFilepicker("image",this._filepickerCallback,this)},this),this._form.one("."+u.INPUTALT).on("keyup",this._handleKeyup,this),i},_autoAdjustSize:function(e,t){var i,n,a,s,o,l,r,h,g,d,m;t=t||!1,i=this._form.one("."+u.INPUTWIDTH),n="width",a=this._form.one("."+u.INPUTHEIGHT),s="height",o=this._form.one("."+u.INPUTCONSTRAIN),l=i.get("value"),r=a.get("value"),h=this._form.one("."+u.IMAGEPREVIEW),this._rawImageDimensions&&(""===l&&(l=this._rawImageDimensions[n],i.set("value",l),l=i.get("value")),h.setStyles({width:null,height:null}),o.get("checked")?(t&&(m=i,i=a,a=m,m=n,n=s,s=m,m=l,l=r,r=m),l.match(I)?(r=l,g=parseInt(l,10),d=this._rawImageDimensions.width/100*g,h.setStyle("width",d),d=this._rawImageDimensions.height/100*g,h.setStyle("height",d)):(r=Math.round(l/this._rawImageDimensions[n]*this._rawImageDimensions[s]),t?h.setStyles({width:r,height:l}):h.setStyles({width:l,height:r})),a.set("value",r)):(l.match(I)?(g=parseInt(l,10),d=this._rawImageDimensions.width/100*g,h.setStyle("width",d+"px")):h.setStyle("width",l+"px"),r.match(I)?(g=parseInt(r,10),d=this._rawImageDimensions.height/100*g,h.setStyle("height",d+"px")):h.setStyle("height",r+"px")))},_filepickerCallback:function(e){""!==e.url&&(this._form.one("."+u.INPUTURL).set("value",e.url),this._form.one("."+u.INPUTWIDTH).set("value",""),this._form.one("."+u.INPUTHEIGHT).set("value",""),this._loadPreviewImage(e.url))},_applyImageProperties:function(t){var e=this._getSelectedImageProperties(),i=t.one("."+u.IMAGEPREVIEW);if(!1===e)return i.setStyle("display","none"),void s.some(function(e){return!!e.isDefault&&(t.one("."+u.INPUTALIGNMENT).set("value",
+e.value),!0)},this);e.align&&t.one("."+u.INPUTALIGNMENT).set("value",e.align),e.customstyle&&t.one("."+u.INPUTCUSTOMSTYLE).set("value",e.customstyle),e.width&&t.one("."+u.INPUTWIDTH).set("value",e.width),e.height&&t.one("."+u.INPUTHEIGHT).set("value",e.height),e.alt&&t.one("."+u.INPUTALT).set("value",e.alt),e.src&&(t.one("."+u.INPUTURL).set("value",e.src),this._loadPreviewImage(e.src)),e.presentation&&t.one("."+u.IMAGEPRESENTATION).set("checked","checked"),this._autoAdjustSize()},_getSelectedImageProperties:function(){var e,t,i,n,a={src:null,alt:null,width:null,height:null,align:"",presentation:!1},s=this.get("host").getSelectedNodes();return(s=s&&s.filter("img"))&&s.size()?(n=this._removeLegacyAlignment(s.item(0)),i=(this._selectedImage=n).getAttribute("style"),a.customstyle=i,(e=n.getAttribute("width")).match(I)||(e=parseInt(e,10)),(t=n.getAttribute("height")).match(I)||(t=parseInt(t,10)),0!==e&&(a.width=e),0!==t&&(a.height=t),this._getAlignmentPropeties(n,a),a.src=n.getAttribute("src"),a.alt=n.getAttribute("alt")||"",a.presentation="presentation"===n.get("role"),a):(this._selectedImage=null,!1)},_getAlignmentPropeties:function(i,n){var a;!s.some(function(e){var t=this._getAlignmentClass(e.value);return i.hasClass(t)?(n.align=e.value,!0):(e.isDefault&&(a=e.value),!1)},this)&&a&&(n.align=a)},_urlChanged:function(){var e=this._form.one("."+u.INPUTURL);""!==e.get("value")&&this._loadPreviewImage(e.get("value"))},_setImage:function(e){var t,i=this._form,n=i.one("."+u.INPUTURL).get("value"),a=i.one("."+u.INPUTALT).get("value"),s=i.one("."+u.INPUTWIDTH).get("value"),o=i.one("."+u.INPUTHEIGHT).get("value"),l=this._getAlignmentClass(i.one("."+u.INPUTALIGNMENT).get("value")),r=i.one("."+u.IMAGEPRESENTATION).get("checked"),h=i.one("."+u.INPUTCONSTRAIN).get("checked"),g=i.one("."+u.INPUTCUSTOMSTYLE).get("value"),d=[],m=this.get("host");if(e.preventDefault(),!this._updateWarning()){if(m.focus(),""!==n){if(this._selectedImage?m.setSelection(m.getSelectionFromNode(this._selectedImage)):m.setSelection(this._currentSelection),h&&d.push(u.RESPONSIVE),d.push(l),!s.match(I)&&isNaN(parseInt(s,10)))return void i.one("."+u.INPUTWIDTH).focus();if(!o.match(I)&&isNaN(parseInt(o,10)))return void i.one("."+u.INPUTHEIGHT).focus();t=c.Handlebars.compile(p)({url:n,alt:a,width:s,height:o,presentation:r,customstyle:g,classlist:d.join(" ")}),this.get("host").insertContentAtFocusPoint(t),this.markUpdated()}this.getDialogue({focusAfterHide:null}).hide()}},_removeLegacyAlignment:function(i){return i.getStyle("margin")&&s.some(function(e){if(i.getStyle(e.name)!==e.value)return!1;var t=c.Node.create("<div>");return t.setStyle("margin",e.margin),i.getStyle("margin")===t.getStyle("margin")&&(i.addClass(this._getAlignmentClass(e.value)),i.setStyle(e.name,null),i.setStyle("margin",null),!0)},this),i},_getAlignmentClass:function(e){return u.ALIGNSETTINGS+"_"+e},_toggleVisibility:function(e,t){var i=this._form,n=i.all(e);n.setStyle("display",t?"block":"none")},_toggleAriaInvalid:function(e,t){var i=this._form;e.forEach(function(e){i.all(e).setAttribute("aria-invalid",t)})},_hasErrorUrlField:function(){var e=this._form,t=e.one("."+u.INPUTURL).get("value"),i=""===t;return this._toggleVisibility("."+u.IMAGEURLWARNING,i),this._toggleAriaInvalid(["."+u.INPUTURL],i),i},_hasErrorAltField:function(){var e=this._form,t=e.one("."+u.INPUTALT).get("value"),i=e.one("."+u.IMAGEPRESENTATION).get("checked"),n=""===t&&!i;return this._toggleVisibility("."+u.IMAGEALTWARNING,n),this._toggleAriaInvalid(["."+u.INPUTALT,"."+u.IMAGEPRESENTATION],n),n},_updateWarning:function(){var e=this._hasErrorUrlField(),t=this._hasErrorAltField(),i=e||t;return this.getDialogue().centerDialogue(),i},_handleKeyup:function(){var e=this._form,t=e.one("."+u.INPUTALT).get("value").length;e.one("#currentcount").setHTML(t)}})},"@VERSION@",{requires:["moodle-editor_atto-plugin"]});
\ No newline at end of file
diff --git a/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button.js b/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button.js
index 418fc17aac7..19cf5db689d 100644
--- a/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button.js
+++ b/lib/editor/atto/plugins/image/yui/build/moodle-atto_image-button/moodle-atto_image-button.js
@@ -92,7 +92,10 @@ var CSS = {
             margin: '0 0 0 0.5em'
         }
     ],
-
+    DEFAULTS = {
+        WIDTH: 160,
+        HEIGHT: 160,
+    },
     REGEX = {
         ISPERCENT: /\d+%/
     },
@@ -550,22 +553,23 @@ Y.namespace('M.atto_image').Button = Y.Base.create('button', Y.M.editor_atto.Edi
         image.onload = function() {
             var input, currentwidth, currentheight, widthRatio, heightRatio;
 
+            // Store dimensions of the raw image, falling back to defaults for images without dimensions (e.g. SVG).
             self._rawImageDimensions = {
-                width: this.width,
-                height: this.height
+                width: this.width || DEFAULTS.WIDTH,
+                height: this.height || DEFAULTS.HEIGHT,
             };
 
             input = self._form.one('.' + CSS.INPUTWIDTH);
             currentwidth = input.get('value');
             if (currentwidth === '') {
-                input.set('value', this.width);
-                currentwidth = "" + this.width;
+                input.set('value', self._rawImageDimensions.width);
+                currentwidth = "" + self._rawImageDimensions.width;
             }
             input = self._form.one('.' + CSS.INPUTHEIGHT);
             currentheight = input.get('value');
             if (currentheight === '') {
-                input.set('value', this.height);
-                currentheight = "" + this.height;
+                input.set('value', self._rawImageDimensions.height);
+                currentheight = "" + self._rawImageDimensions.height;
             }
             input = self._form.one('.' + CSS.IMAGEPREVIEW);
             input.setAttribute('src', this.src);
@@ -576,13 +580,10 @@ Y.namespace('M.atto_image').Button = Y.Base.create('button', Y.M.editor_atto.Edi
             input = self._form.one('.' + CSS.INPUTCONSTRAIN);
             if (currentwidth.match(REGEX.ISPERCENT) && currentheight.match(REGEX.ISPERCENT)) {
                 input.set('checked', currentwidth === currentheight);
+            } else if (this.width === 0 || this.height === 0) {
+                // If we don't have both dimensions of the image, we can't auto-size it, so disable control.
+                input.set('disabled', 'disabled');
             } else {
-                if (this.width === 0) {
-                    this.width = 1;
-                }
-                if (this.height === 0) {
-                    this.height = 1;
-                }
                 // This is the same as comparing to 3 decimal places.
                 widthRatio = Math.round(1000 * parseInt(currentwidth, 10) / this.width);
                 heightRatio = Math.round(1000 * parseInt(currentheight, 10) / this.height);
diff --git a/lib/editor/atto/plugins/image/yui/src/button/js/button.js b/lib/editor/atto/plugins/image/yui/src/button/js/button.js
index c41fcdfc67b..46aad7bce8d 100644
--- a/lib/editor/atto/plugins/image/yui/src/button/js/button.js
+++ b/lib/editor/atto/plugins/image/yui/src/button/js/button.js
@@ -90,7 +90,10 @@ var CSS = {
             margin: '0 0 0 0.5em'
         }
     ],
-
+    DEFAULTS = {
+        WIDTH: 160,
+        HEIGHT: 160,
+    },
     REGEX = {
         ISPERCENT: /\d+%/
     },
@@ -548,22 +551,23 @@ Y.namespace('M.atto_image').Button = Y.Base.create('button', Y.M.editor_atto.Edi
         image.onload = function() {
             var input, currentwidth, currentheight, widthRatio, heightRatio;
 
+            // Store dimensions of the raw image, falling back to defaults for images without dimensions (e.g. SVG).
             self._rawImageDimensions = {
-                width: this.width,
-                height: this.height
+                width: this.width || DEFAULTS.WIDTH,
+                height: this.height || DEFAULTS.HEIGHT,
             };
 
             input = self._form.one('.' + CSS.INPUTWIDTH);
             currentwidth = input.get('value');
             if (currentwidth === '') {
-                input.set('value', this.width);
-                currentwidth = "" + this.width;
+                input.set('value', self._rawImageDimensions.width);
+                currentwidth = "" + self._rawImageDimensions.width;
             }
             input = self._form.one('.' + CSS.INPUTHEIGHT);
             currentheight = input.get('value');
             if (currentheight === '') {
-                input.set('value', this.height);
-                currentheight = "" + this.height;
+                input.set('value', self._rawImageDimensions.height);
+                currentheight = "" + self._rawImageDimensions.height;
             }
             input = self._form.one('.' + CSS.IMAGEPREVIEW);
             input.setAttribute('src', this.src);
@@ -574,13 +578,10 @@ Y.namespace('M.atto_image').Button = Y.Base.create('button', Y.M.editor_atto.Edi
             input = self._form.one('.' + CSS.INPUTCONSTRAIN);
             if (currentwidth.match(REGEX.ISPERCENT) && currentheight.match(REGEX.ISPERCENT)) {
                 input.set('checked', currentwidth === currentheight);
+            } else if (this.width === 0 || this.height === 0) {
+                // If we don't have both dimensions of the image, we can't auto-size it, so disable control.
+                input.set('disabled', 'disabled');
             } else {
-                if (this.width === 0) {
-                    this.width = 1;
-                }
-                if (this.height === 0) {
-                    this.height = 1;
-                }
                 // This is the same as comparing to 3 decimal places.
                 widthRatio = Math.round(1000 * parseInt(currentwidth, 10) / this.width);
                 heightRatio = Math.round(1000 * parseInt(currentheight, 10) / this.height);