diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6ef93a2d7c..e31a6c021d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,7 +4,11 @@ HumHub Changelog
 1.13.2 (Unreleased)
 -------------------------
 - Fix #5965: Suppress log warning 'Invalid session auth key attempted for user'
-
+- Fix #6084: Automatic LDAP user registration broken when not all req. attributes provided
+- Fix #6104: Fix update user with not existing group
+- Fix #6103: Fix null passing to parse_str()
+- Fix #6108: Fix log time in the `date()` function
+- Fix #6122: Fix deleting a content with empty reason
 
 1.13.1 (January 25, 2023)
 -------------------------
diff --git a/protected/humhub/modules/admin/controllers/SettingController.php b/protected/humhub/modules/admin/controllers/SettingController.php
index 3cd8e741c9..7675403b41 100644
--- a/protected/humhub/modules/admin/controllers/SettingController.php
+++ b/protected/humhub/modules/admin/controllers/SettingController.php
@@ -314,7 +314,7 @@ class SettingController extends Controller
 
         // I wish..
         if ($dating) {
-            $dating = date('Y-m-d H:i:s', $dating->log_time);
+            $dating = date('Y-m-d H:i:s', (int) $dating->log_time);
         } else {
             $dating = "the begining of time";
         }
diff --git a/protected/humhub/modules/admin/controllers/UserController.php b/protected/humhub/modules/admin/controllers/UserController.php
index f4ed16e51e..5345f0b8a7 100644
--- a/protected/humhub/modules/admin/controllers/UserController.php
+++ b/protected/humhub/modules/admin/controllers/UserController.php
@@ -149,7 +149,8 @@ class UserController extends Controller
                     'items' => UserEditForm::getGroupItems(),
                     'options' => [
                         'data-placeholder' => Yii::t('AdminModule.user', 'Select Groups'),
-                        'data-placeholder-more' => Yii::t('AdminModule.user', 'Add Groups...')
+                        'data-placeholder-more' => Yii::t('AdminModule.user', 'Add Groups...'),
+                        'data-tags' => 'false'
                     ],
                     'maxSelection' => 250,
                     'isVisible' => Yii::$app->user->can(new ManageGroups())
diff --git a/protected/humhub/modules/admin/models/forms/UserEditForm.php b/protected/humhub/modules/admin/models/forms/UserEditForm.php
index ff436af763..78418f6988 100644
--- a/protected/humhub/modules/admin/models/forms/UserEditForm.php
+++ b/protected/humhub/modules/admin/models/forms/UserEditForm.php
@@ -2,12 +2,11 @@
 
 namespace humhub\modules\admin\models\forms;
 
-use humhub\libs\Html;
-use humhub\modules\user\models\GroupUser;
-use Yii;
-use humhub\modules\user\models\User;
-use humhub\modules\user\models\Group;
 use humhub\modules\admin\permissions\ManageGroups;
+use humhub\modules\user\models\Group;
+use humhub\modules\user\models\GroupUser;
+use humhub\modules\user\models\User;
+use Yii;
 
 /**
  * Description of UserEditForm
@@ -18,14 +17,13 @@ class UserEditForm extends User
 {
     /**
      * GroupId selection array of the form.
-     * @var type
+     * @var array
      */
     public $groupSelection;
 
     /**
      * Current member groups (models) of the given $user
-     * @var type
-     *
+     * @var Group[]
      */
     public $currentGroups;
 
@@ -103,19 +101,19 @@ class UserEditForm extends User
                 if (!$this->isCurrentlyMemberOf($groupId)) {
                     /* @var $group Group */
                     $group = Group::findOne(['id' => $groupId]);
-                    if(!$group->is_admin_group || Yii::$app->user->isAdmin()) {
+                    if ($group && (!$group->is_admin_group || Yii::$app->user->isAdmin())) {
                         $group->addUser($this);
                     }
                 }
             }
         }
 
-        return parent::afterSave($insert, $changedAttributes);
+        parent::afterSave($insert, $changedAttributes);
     }
 
     /**
      * Checks if the given group (id or model object) is contained in the form selection
-     * @param integer $groupId groupId or Group model object
+     * @param int|Group $groupId groupId or Group model object
      * @return boolean true if contained in selection else false
      */
     private function isInGroupSelection($groupId)
diff --git a/protected/humhub/modules/admin/views/setting/oembed_edit.php b/protected/humhub/modules/admin/views/setting/oembed_edit.php
index b84a1fba0a..51306310ef 100644
--- a/protected/humhub/modules/admin/views/setting/oembed_edit.php
+++ b/protected/humhub/modules/admin/views/setting/oembed_edit.php
@@ -9,7 +9,7 @@ use yii\web\View;
 /* @var $name string */
 /** @var OEmbedProviderForm $model */
 
-parse_str($model->endpoint, $query);
+parse_str($model->endpoint ?? '', $query);
 
 $this->registerJs(<<<JS
     function initEndpointInputs() {
diff --git a/protected/humhub/modules/content/controllers/ContentController.php b/protected/humhub/modules/content/controllers/ContentController.php
index 1404f53ec6..46c3fec4c5 100644
--- a/protected/humhub/modules/content/controllers/ContentController.php
+++ b/protected/humhub/modules/content/controllers/ContentController.php
@@ -13,18 +13,13 @@ use humhub\components\Controller;
 use humhub\modules\content\models\Content;
 use humhub\modules\content\models\forms\AdminDeleteContentForm;
 use humhub\modules\content\Module;
-use humhub\modules\content\notifications\ContentDeleted;
 use humhub\modules\content\permissions\CreatePublicContent;
 use humhub\modules\content\widgets\AdminDeleteModal;
 use humhub\modules\stream\actions\StreamEntryResponse;
 use Yii;
-use yii\base\BaseObject;
 use yii\base\Exception;
 use yii\base\InvalidConfigException;
-use yii\web\BadRequestHttpException;
 use yii\web\ForbiddenHttpException;
-use yii\web\HttpException;
-use yii\web\NotAcceptableHttpException;
 use yii\web\NotFoundHttpException;
 use yii\web\Response;
 
@@ -57,17 +52,15 @@ class ContentController extends Controller
      */
     public function actionDelete()
     {
-        Yii::$app->response->format = 'json';
-
         $this->forcePostRequest();
 
         $model = Yii::$app->request->get('model');
 
         // Due to backward compatibility we use the old delete mechanism in case a model parameter is provided
-        $id = (int)($model != null) ? Yii::$app->request->get('id') : Yii::$app->request->post('id');
+        $id = $model ? Yii::$app->request->get('id') : Yii::$app->request->post('id');
 
-        /* @var $contentObjs Content */
-        $contentObj = ($model != null) ? Content::Get($model, $id) : Content::findOne(['id' => $id]);
+        /* @var $contentObj Content */
+        $contentObj = $model ? Content::Get($model, $id) : Content::findOne(['id' => $id]);
 
         if (!$contentObj) {
             throw new NotFoundHttpException();
@@ -77,37 +70,19 @@ class ContentController extends Controller
             throw new ForbiddenHttpException();
         }
 
-        if ($contentObj !== null) {
-            $form = new AdminDeleteContentForm();
+        $form = new AdminDeleteContentForm(['content' => $contentObj]);
+        $form->load(Yii::$app->request->post());
 
-            if ($form->load(Yii::$app->request->post())) {
-                if (!$form->validate()) {
-                    throw new BadRequestHttpException();
-                }
-
-                if ($form->notify) {
-                    $contentDeleted = ContentDeleted::instance()
-                        ->from(Yii::$app->user->getIdentity())
-                        ->payload(['contentTitle' => (new ContentDeleted)->getContentPlainTextInfo($contentObj), 'reason' => $form->message]);
-                    $contentDeleted->saveRecord($contentObj->createdBy);
-
-                    $contentDeleted->record->updateAttributes([
-                        'send_web_notifications' => 1
-                    ]);
-                }
-            }
-
-            $json = [
-                'success' => $contentObj->softDelete(),
-                'uniqueId' => $contentObj->getUniqueId(),
-                'model' => $model,
-                'pk' => $id
-            ];
-        } else {
-            throw new HttpException(500, Yii::t('ContentModule.base', 'Could not delete content!'));
+        if (!$form->delete()) {
+            return $this->asJson(['error' => $form->getErrorsAsString()]);
         }
 
-        return $json;
+        return $this->asJson([
+            'success' => true,
+            'uniqueId' => $contentObj->getUniqueId(),
+            'model' => $model,
+            'pk' => $id
+        ]);
     }
 
     /**
@@ -126,7 +101,7 @@ class ContentController extends Controller
         }
 
         if (!$contentObj->canEdit()) {
-            throw new HttpException(400);
+            throw new ForbiddenHttpException();
         }
 
         return [
@@ -192,9 +167,7 @@ class ContentController extends Controller
     {
         $this->forcePostRequest();
 
-        $post = Yii::$app->request->post();
-
-        $content = Content::findOne(['id' => $post['id']]);
+        $content = Content::findOne(['id' => Yii::$app->request->post('id')]);
 
         if (!$content) {
             throw new NotFoundHttpException();
@@ -204,26 +177,14 @@ class ContentController extends Controller
             throw new ForbiddenHttpException();
         }
 
-        $form = new AdminDeleteContentForm();
+        $form = new AdminDeleteContentForm(['content' => $content]);
+        $form->load(Yii::$app->request->post());
 
-        if ($form->load($post)) {
-            if (!$form->validate()) {
-                throw new BadRequestHttpException();
-            }
-
-            if ($form->notify) {
-                $contentDeleted = ContentDeleted::instance()
-                    ->from(Yii::$app->user->getIdentity())
-                    ->payload(['contentTitle' => (new ContentDeleted)->getContentPlainTextInfo($content), 'reason' => $form->message]);
-                $contentDeleted->saveRecord($content->createdBy);
-
-                $contentDeleted->record->updateAttributes([
-                    'send_web_notifications' => 1
-                ]);
-            }
+        if (!$form->delete()) {
+            return $this->asJson(['error' => $form->getErrorsAsString()]);
         }
 
-        return $this->asJson(['success' => $content->softDelete()]);
+        return $this->asJson(['success' => true]);
     }
 
     public function actionReload($id)
@@ -231,11 +192,11 @@ class ContentController extends Controller
         $content = Content::findOne(['id' => $id]);
 
         if (!$content) {
-            throw new HttpException(400, Yii::t('ContentModule.base', 'Invalid content id given!'));
+            throw new NotFoundHttpException(Yii::t('ContentModule.base', 'Invalid content id given!'));
         }
 
         if (!$content->canView()) {
-            throw new HttpException(403);
+            throw new ForbiddenHttpException();
         }
 
         return StreamEntryResponse::getAsJson($content);
@@ -244,10 +205,9 @@ class ContentController extends Controller
     /**
      * Switches the content visibility for the given content.
      *
-     * @param type $id content id
+     * @param int $id content id
      * @return Response
      * @throws Exception
-     * @throws HttpException
      * @throws InvalidConfigException
      * @throws \Throwable
      * @throws \yii\db\IntegrityException
@@ -258,11 +218,11 @@ class ContentController extends Controller
         $content = Content::findOne(['id' => $id]);
 
         if (!$content) {
-            throw new HttpException(400, Yii::t('ContentModule.base', 'Invalid content id given!'));
+            throw new NotFoundHttpException(Yii::t('ContentModule.base', 'Invalid content id given!'));
         } elseif (!$content->canEdit()) {
-            throw new HttpException(403);
+            throw new ForbiddenHttpException();
         } elseif ($content->isPrivate() && !$content->container->permissionManager->can(new CreatePublicContent())) {
-            throw new HttpException(403);
+            throw new ForbiddenHttpException();
         }
 
         if ($content->isPrivate()) {
@@ -284,7 +244,6 @@ class ContentController extends Controller
      * @param bool $lockComments True to lock comments, False to unlock
      * @return Response
      * @throws Exception
-     * @throws HttpException
      * @throws InvalidConfigException
      * @throws \Throwable
      * @throws \yii\db\IntegrityException
@@ -295,9 +254,9 @@ class ContentController extends Controller
         $content = Content::findOne(['id' => $id]);
 
         if (!$content) {
-            throw new HttpException(400, Yii::t('ContentModule.base', 'Invalid content id given!'));
+            throw new NotFoundHttpException(Yii::t('ContentModule.base', 'Invalid content id given!'));
         } elseif (!$content->canLockComments()) {
-            throw new HttpException(403);
+            throw new ForbiddenHttpException();
         }
 
         $content->locked_comments = $lockComments;
@@ -313,7 +272,6 @@ class ContentController extends Controller
      * @param int $id Content id
      * @return Response
      * @throws Exception
-     * @throws HttpException
      * @throws InvalidConfigException
      * @throws \Throwable
      * @throws \yii\db\IntegrityException
@@ -329,7 +287,6 @@ class ContentController extends Controller
      * @param int $id Content id
      * @return Response
      * @throws Exception
-     * @throws HttpException
      * @throws InvalidConfigException
      * @throws \Throwable
      * @throws \yii\db\IntegrityException
@@ -345,7 +302,6 @@ class ContentController extends Controller
      * Returns JSON Output.
      * @return Response
      * @throws ForbiddenHttpException
-     * @throws HttpException
      * @throws NotFoundHttpException
      * @throws Exception
      * @throws InvalidConfigException
diff --git a/protected/humhub/modules/content/models/forms/AdminDeleteContentForm.php b/protected/humhub/modules/content/models/forms/AdminDeleteContentForm.php
index cc469d2899..9d9070fdad 100644
--- a/protected/humhub/modules/content/models/forms/AdminDeleteContentForm.php
+++ b/protected/humhub/modules/content/models/forms/AdminDeleteContentForm.php
@@ -2,8 +2,8 @@
 
 namespace humhub\modules\content\models\forms;
 
-use humhub\modules\content\components\ContentActiveRecord;
 use humhub\modules\content\models\Content;
+use humhub\modules\content\notifications\ContentDeleted;
 use Yii;
 use yii\base\Model;
 
@@ -12,6 +12,11 @@ use yii\base\Model;
  */
 class AdminDeleteContentForm extends Model
 {
+    /**
+     * @var Content
+     */
+    public $content;
+
     /**
      * @var string
      */
@@ -43,4 +48,46 @@ class AdminDeleteContentForm extends Model
             'notify' => Yii::t('CommentModule.base', 'Send a notification to author')
         ];
     }
+
+    public function delete(): bool
+    {
+        if (!$this->validate()) {
+            return false;
+        }
+
+        if (!$this->notify()) {
+            return false;
+        }
+
+        return (bool) $this->content->softDelete();
+    }
+
+    public function notify(): bool
+    {
+        if (!$this->notify) {
+            return true;
+        }
+
+        $contentDeleted = ContentDeleted::instance()
+            ->from(Yii::$app->user->getIdentity())
+            ->payload([
+                'contentTitle' => (new ContentDeleted)->getContentPlainTextInfo($this->content),
+                'reason' => $this->message
+            ]);
+        if (!$contentDeleted->saveRecord($this->content->createdBy)) {
+            $this->addError('message', Yii::t('ContentModule.base', 'Cannot notify the author.'));
+            return false;
+        }
+
+        $contentDeleted->record->updateAttributes([
+            'send_web_notifications' => 1
+        ]);
+
+        return true;
+    }
+
+    public function getErrorsAsString(): string
+    {
+        return implode(' ', $this->getErrorSummary(true));
+    }
 }
diff --git a/protected/humhub/modules/content/resources/js/humhub.content.js b/protected/humhub/modules/content/resources/js/humhub.content.js
index 4994434c6a..a07c1e0d6e 100644
--- a/protected/humhub/modules/content/resources/js/humhub.content.js
+++ b/protected/humhub/modules/content/resources/js/humhub.content.js
@@ -7,12 +7,12 @@
 humhub.module('content', function (module, require, $) {
     var client = require('client');
     var util = require('util');
-    var object = util.object;
     var string = util.string;
     var actions = require('action');
     var Component = actions.Component;
     var event = require('event');
     var modal = require('ui.modal');
+    var status = require('ui.status');
 
     var DATA_CONTENT_KEY = "content-key";
     var DATA_CONTENT_DELETE_URL = "content-delete-url";
@@ -130,9 +130,13 @@ humhub.module('content', function (module, require, $) {
             client.post(deleteUrl, {
                 data: postData
             }).then(function (response) {
-                that.remove().then(function () {
-                    resolve(true);
-                });
+                if (response.response.success) {
+                    that.remove().then(function () {
+                        resolve(true);
+                    });
+                } else {
+                    status.error(response.response.error);
+                }
             }).catch(function (err) {
                 reject(err);
             }).finally(function () {
diff --git a/protected/humhub/modules/ldap/authclient/LdapAuth.php b/protected/humhub/modules/ldap/authclient/LdapAuth.php
index cc9d4aee54..76dc9add95 100644
--- a/protected/humhub/modules/ldap/authclient/LdapAuth.php
+++ b/protected/humhub/modules/ldap/authclient/LdapAuth.php
@@ -579,4 +579,15 @@ class LdapAuth extends BaseFormAuth implements AutoSyncUsers, SyncAttributes, Ap
 
         return $authClient;
     }
+
+    /**
+     * @inheridoc
+     */
+    public function beforeSerialize(): void
+    {
+        // Make sure we normalized user attributes before put it in session (anonymous functions)
+        $this->setNormalizeUserAttributeMap([]);
+
+        $this->_ldap = null;
+    }
 }
diff --git a/protected/humhub/modules/user/authclient/BaseClient.php b/protected/humhub/modules/user/authclient/BaseClient.php
index 1dcc906b01..678309e8c5 100644
--- a/protected/humhub/modules/user/authclient/BaseClient.php
+++ b/protected/humhub/modules/user/authclient/BaseClient.php
@@ -34,7 +34,15 @@ class BaseClient extends \yii\authclient\BaseClient
      */
     protected function initUserAttributes()
     {
-        
+
     }
 
+    /**
+     * Workaround for serialization into session during the registration process
+     *
+     * @return void
+     */
+    public function beforeSerialize(): void
+    {
+    }
 }
diff --git a/protected/humhub/modules/user/controllers/AuthController.php b/protected/humhub/modules/user/controllers/AuthController.php
index 50c80a9e99..b236f30158 100644
--- a/protected/humhub/modules/user/controllers/AuthController.php
+++ b/protected/humhub/modules/user/controllers/AuthController.php
@@ -36,7 +36,7 @@ class AuthController extends Controller
      * after the response is generated.
      */
     const EVENT_AFTER_LOGIN = 'afterLogin';
-    
+
     /**
      * @event Triggered after an successful login but before checking user status
      */
@@ -192,8 +192,10 @@ class AuthController extends Controller
             return $this->login($user, $authClient);
         }
 
-        // Make sure we normalized user attributes before put it in session (anonymous functions)
-        $authClient->setNormalizeUserAttributeMap([]);
+        if ($authClient instanceof \humhub\modules\user\authclient\BaseClient) {
+            /** @var \humhub\modules\user\authclient\BaseClient $authClient */
+            $authClient->beforeSerialize();
+        }
 
         // Store authclient in session - for registration controller
         Yii::$app->session->set('authClient', $authClient);