diff --git a/admin/environment.xml b/admin/environment.xml
index 55a1aee8825..13c205a665e 100644
--- a/admin/environment.xml
+++ b/admin/environment.xml
@@ -3729,6 +3729,8 @@
           <ON_CHECK message="iscustomadminwarnings" />
         </FEEDBACK>
       </CUSTOM_CHECK>
+      <CUSTOM_CHECK file="lib/upgradelib.php" function="check_xmlrpc_usage" level="optional">
+      </CUSTOM_CHECK>
     </CUSTOM_CHECKS>
   </MOODLE>
 </COMPATIBILITY_MATRIX>
diff --git a/admin/index.php b/admin/index.php
index 943fea85259..c8c9015d188 100644
--- a/admin/index.php
+++ b/admin/index.php
@@ -916,6 +916,12 @@ $showfeedbackencouragement = empty($CFG->enableuserfeedback);
 // Check if the service and support content setting is enabled or not.
 $servicesandsupportcontent = !isset($CFG->showservicesandsupportcontent) || $CFG->showservicesandsupportcontent;
 
+// Check whether the XML-RPC protocol is enabled or not.
+require_once($CFG->libdir . '/environmentlib.php');
+$result = new environment_results('custom_checks');
+$result = check_xmlrpc_usage($result);
+$xmlrpcwarning = !is_null($result) ? get_string($result->getFeedbackStr(), 'admin') : '';
+
 admin_externalpage_setup('adminnotifications');
 
 $output = $PAGE->get_renderer('core', 'admin');
@@ -924,4 +930,5 @@ echo $output->admin_notifications_page($maturity, $insecuredataroot, $errorsdisp
                                        $maintenancemode, $availableupdates, $availableupdatesfetch, $buggyiconvnomb,
                                        $registered, $cachewarnings, $eventshandlers, $themedesignermode, $devlibdir,
                                        $mobileconfigured, $overridetossl, $invalidforgottenpasswordurl, $croninfrequent,
-                                       $showcampaigncontent, $showfeedbackencouragement, $servicesandsupportcontent);
+                                       $showcampaigncontent, $showfeedbackencouragement, $servicesandsupportcontent,
+                                       $xmlrpcwarning);
diff --git a/admin/mnet/access_control.php b/admin/mnet/access_control.php
index a1223012b77..edb3b06d322 100644
--- a/admin/mnet/access_control.php
+++ b/admin/mnet/access_control.php
@@ -117,6 +117,7 @@ if ($form = data_submitted() and confirm_sesskey()) {
 }
 
 echo $OUTPUT->header();
+echo $OUTPUT->render(mnet_get_deprecation_notice());
 
 // Explain
 echo $OUTPUT->box(get_string('ssoacldescr','mnet'));
diff --git a/admin/mnet/index.php b/admin/mnet/index.php
index fff93869420..5e0240b8582 100644
--- a/admin/mnet/index.php
+++ b/admin/mnet/index.php
@@ -81,6 +81,7 @@
     $hosts = $DB->get_records_select('mnet_host', "id <> ? AND deleted = 0", array($CFG->mnet_localhost_id), 'wwwroot ASC');
 
     echo $OUTPUT->header();
+    echo $OUTPUT->render(mnet_get_deprecation_notice());
 ?>
 <form method="post" action="index.php">
     <table align="center" width="635" class="generaltable" border="0" cellpadding="5" cellspacing="0">
diff --git a/admin/mnet/peers.php b/admin/mnet/peers.php
index 49fd346493a..348a6243f86 100644
--- a/admin/mnet/peers.php
+++ b/admin/mnet/peers.php
@@ -51,6 +51,8 @@ if ($hostid && $DB->get_field('mnet_host', 'deleted', array('id' => $hostid)) !=
 $PAGE->set_url('/admin/mnet/peers.php');
 admin_externalpage_setup($adminsection);
 
+$deprecatenotify = mnet_get_deprecation_notice();
+
 if (!extension_loaded('openssl')) {
     print_error('requiresopenssl', 'mnet');
 }
@@ -90,6 +92,7 @@ if ($formdata = $simpleform->get_data()) {
     $formdata->oldpublickey = $mnet_peer->public_key; // set this so we can confirm on form post without having to recreate the mnet_peer object
     $reviewform->set_data($mnet_peer);
     echo $OUTPUT->header();
+    echo $OUTPUT->render($deprecatenotify);
     echo $OUTPUT->box_start();
     $reviewform->display();
     echo $OUTPUT->box_end();
@@ -177,6 +180,7 @@ if ($formdata = $reviewform->get_data()) {
     }
 } else if ($reviewform->is_submitted()) { // submitted, but errors
     echo $OUTPUT->header();
+    echo $OUTPUT->render($deprecatenotify);
     echo $OUTPUT->box_start();
     $reviewform->display();
     echo $OUTPUT->box_end();
@@ -187,6 +191,7 @@ if ($formdata = $reviewform->get_data()) {
 
 // normal flow - just display all hosts with links
 echo $OUTPUT->header();
+echo $OUTPUT->render($deprecatenotify);
 $hosts = mnet_get_hosts(true);
 
 // print the table to display the register all hosts setting
diff --git a/admin/mnet/tabs.php b/admin/mnet/tabs.php
index 0107d758285..bf0c8ff3e3a 100644
--- a/admin/mnet/tabs.php
+++ b/admin/mnet/tabs.php
@@ -44,4 +44,5 @@ if (isset($mnet_peer->id) && $mnet_peer->id > 0) {
 } else {
     $tabs[] = new tabobject('mnetdetails', '#', $strmnetedithost, $strmnetedithost, false);
 }
+echo $OUTPUT->render(mnet_get_deprecation_notice());
 print_tabs(array($tabs), $currenttab);
diff --git a/admin/mnet/trustedhosts.html b/admin/mnet/trustedhosts.html
index e48a3d3b542..951e8b91852 100644
--- a/admin/mnet/trustedhosts.html
+++ b/admin/mnet/trustedhosts.html
@@ -1,5 +1,6 @@
 <?php
 echo $OUTPUT->header();
+echo $OUTPUT->render(mnet_get_deprecation_notice());
 ?>
 <div id="trustedhosts"><!-- See theme/standard/styles_layout.css #trustedhosts .generaltable for rules -->
 <table cellspacing="0" cellpadding="5"  class="generaltable generalbox" >
diff --git a/admin/renderer.php b/admin/renderer.php
index cbab1a2af2e..11fa0a16da5 100644
--- a/admin/renderer.php
+++ b/admin/renderer.php
@@ -285,6 +285,7 @@ class core_admin_renderer extends plugin_renderer_base {
      * @param bool $showcampaigncontent Whether the campaign content should be visible or not.
      * @param bool $showfeedbackencouragement Whether the feedback encouragement content should be displayed or not.
      * @param bool $showservicesandsupport Whether the services and support content should be displayed or not.
+     * @param string $xmlrpcwarning XML-RPC deprecation warning message.
      *
      * @return string HTML to output.
      */
@@ -293,7 +294,8 @@ class core_admin_renderer extends plugin_renderer_base {
             $buggyiconvnomb, $registered, array $cachewarnings = array(), $eventshandlers = 0,
             $themedesignermode = false, $devlibdir = false, $mobileconfigured = false,
             $overridetossl = false, $invalidforgottenpasswordurl = false, $croninfrequent = false,
-            $showcampaigncontent = false, bool $showfeedbackencouragement = false, bool $showservicesandsupport = false) {
+            $showcampaigncontent = false, bool $showfeedbackencouragement = false, bool $showservicesandsupport = false,
+            $xmlrpcwarning = '') {
 
         global $CFG;
         $output = '';
@@ -317,6 +319,7 @@ class core_admin_renderer extends plugin_renderer_base {
         $output .= $this->registration_warning($registered);
         $output .= $this->mobile_configuration_warning($mobileconfigured);
         $output .= $this->forgotten_password_url_warning($invalidforgottenpasswordurl);
+        $output .= $this->mnet_deprecation_warning($xmlrpcwarning);
         $output .= $this->userfeedback_encouragement($showfeedbackencouragement);
         $output .= $this->services_and_support_content($showservicesandsupport);
         $output .= $this->campaign_content($showcampaigncontent);
@@ -2238,4 +2241,18 @@ class core_admin_renderer extends plugin_renderer_base {
 
         return $output;
     }
+
+    /**
+     * Display a warning about the deprecation of Mnet.
+     *
+     * @param string $xmlrpcwarning The warning message
+     * @return string HTML to output.
+     */
+    protected function mnet_deprecation_warning($xmlrpcwarning) {
+        if (empty($xmlrpcwarning)) {
+            return '';
+        }
+
+        return $this->warning($xmlrpcwarning);
+    }
 }
diff --git a/admin/settings/mnet.php b/admin/settings/mnet.php
index 9bb5b15dd4a..f853938c50a 100644
--- a/admin/settings/mnet.php
+++ b/admin/settings/mnet.php
@@ -49,6 +49,8 @@ $ADMIN->add('mnet', new admin_externalpage('trustedhosts', new lang_string('trus
 if (isset($CFG->mnet_dispatcher_mode) and $CFG->mnet_dispatcher_mode !== 'off') {
     $profilefields = new admin_settingpage('mnetprofilefields', new lang_string('profilefields', 'mnet'),
                                                'moodle/site:config');
+    $profilefields->add(new admin_setting_heading('mnetprofilefields/xmlrpcmnet', '',
+        $OUTPUT->render(mnet_get_deprecation_notice())));
     $ADMIN->add('mnet', $profilefields);
 
     $fields = mnet_profile_field_options();
diff --git a/auth/mnet/settings.php b/auth/mnet/settings.php
index b7aa4a4b59a..fae2ab9f4c4 100644
--- a/auth/mnet/settings.php
+++ b/auth/mnet/settings.php
@@ -27,6 +27,11 @@ defined('MOODLE_INTERNAL') || die;
 if ($ADMIN->fulltree) {
     require_once($CFG->dirroot.'/lib/outputlib.php');
 
+    $notify = new \core\output\notification(get_string('xmlrpcmnetauthenticationenabled', 'admin'),
+        \core\output\notification::NOTIFY_WARNING);
+    $settings->add(new admin_setting_heading('auth_mnet/xmlrpcmnet', '',
+        $OUTPUT->render($notify)));
+
     // Introductory explanation.
     $settings->add(new admin_setting_heading('auth_mnet/pluginname', '',
             new lang_string('auth_mnetdescription', 'auth_mnet')));
diff --git a/lang/en/admin.php b/lang/en/admin.php
index 4bdd1f9d9c6..63be120f158 100644
--- a/lang/en/admin.php
+++ b/lang/en/admin.php
@@ -1524,6 +1524,10 @@ $string['warningiconvbuggy'] = 'Your version of the iconv library does not suppo
 $string['webproxy'] = 'Web proxy';
 $string['webproxyinfo'] = 'Fill in the following options if your Moodle server cannot access the internet directly. Internet access is required for the download of environment data, language packs, RSS feeds, timezones, etc.<br /><em>The PHP cURL extension is highly recommended.</em>';
 $string['xmlrpcrecommended'] = 'The XMLRPC extension is useful for web services and Moodle networking.';
+$string['xmlrpcmaharaenabled'] = 'It has been detected that the Mahara ePortfolio is enabled on your site. This feature relies on the PHP XML-RPC extension which is no longer supported by PHP.';
+$string['xmlrpcmnetauthenticationenabled'] = 'It has been detected that the MNet authentication is enabled on your site. This feature relies on the PHP XML-RPC extension which is no longer supported by PHP.';
+$string['xmlrpcmnetenabled'] = 'It has been detected that the Moodle Networking is enabled on your site. This feature relies on the PHP XML-RPC extension which is no longer supported by PHP.';
+$string['xmlrpcwebserviceenabled'] = 'It has been detected that the XML-RPC Web Service protocol is enabled on your site. This feature relies on the PHP XML-RPC extension which is no longer supported by PHP.';
 $string['yuicomboloading'] = 'YUI combo loading';
 $string['ziprequired'] = 'The Zip PHP extension is now required by Moodle, info-ZIP binaries or PclZip library are not used anymore.';
 $string['manageqbanks'] = 'Manage question bank plugins';
diff --git a/lib/adminlib.php b/lib/adminlib.php
index 649f2b283b3..fdc812747e7 100644
--- a/lib/adminlib.php
+++ b/lib/adminlib.php
@@ -7138,6 +7138,11 @@ class admin_setting_manageauths extends admin_setting {
         }
 
         $return = $OUTPUT->heading(get_string('actauthhdr', 'auth'), 3, 'main');
+        if (in_array('mnet', $authsenabled)) {
+            $notify = new \core\output\notification(get_string('xmlrpcmnetauthenticationenabled', 'admin'),
+                \core\output\notification::NOTIFY_WARNING);
+            $return .= $OUTPUT->render($notify);
+        }
         $return .= $OUTPUT->box_start('generalbox authsui');
 
         $table = new html_table();
@@ -10382,16 +10387,21 @@ class admin_setting_managewebserviceprotocols extends admin_setting {
         $strversion = get_string('version');
 
         $protocols_available = core_component::get_plugin_list('webservice');
-        $active_protocols = empty($CFG->webserviceprotocols) ? array() : explode(',', $CFG->webserviceprotocols);
+        $activeprotocols = empty($CFG->webserviceprotocols) ? array() : explode(',', $CFG->webserviceprotocols);
         ksort($protocols_available);
 
-        foreach ($active_protocols as $key=>$protocol) {
+        foreach ($activeprotocols as $key => $protocol) {
             if (empty($protocols_available[$protocol])) {
-                unset($active_protocols[$key]);
+                unset($activeprotocols[$key]);
             }
         }
 
         $return = $OUTPUT->heading(get_string('actwebserviceshhdr', 'webservice'), 3, 'main');
+        if (in_array('xmlrpc', $activeprotocols)) {
+            $notify = new \core\output\notification(get_string('xmlrpcwebserviceenabled', 'admin'),
+                \core\output\notification::NOTIFY_WARNING);
+            $return .= $OUTPUT->render($notify);
+        }
         $return .= $OUTPUT->box_start('generalbox webservicesui');
 
         $table = new html_table();
@@ -10413,7 +10423,7 @@ class admin_setting_managewebserviceprotocols extends admin_setting {
             $version = isset($plugin->version) ? $plugin->version : '';
 
             // hide/show link
-            if (in_array($protocol, $active_protocols)) {
+            if (in_array($protocol, $activeprotocols)) {
                 $hideshow = "<a href=\"$url&amp;action=disable&amp;webservice=$protocol\">";
                 $hideshow .= $OUTPUT->pix_icon('t/hide', $strdisable) . '</a>';
                 $displayname = "<span>$name</span>";
diff --git a/lib/tests/upgradelib_test.php b/lib/tests/upgradelib_test.php
index 0e1ce803cd0..80851dcff6e 100644
--- a/lib/tests/upgradelib_test.php
+++ b/lib/tests/upgradelib_test.php
@@ -1526,4 +1526,97 @@ class upgradelib_test extends advanced_testcase {
         $this->assertEquals('admin_dir_usage', $result->getInfo());
         $this->assertFalse($result->getStatus());
     }
+
+    /**
+     * Test the check_xmlrpc_usage check when the XML-RPC web service method is not set.
+     *
+     * @return void
+     */
+    public function test_check_xmlrpc_webservice_is_not_set(): void {
+        global $CFG;
+
+        $this->resetAfterTest();
+
+        $result = new environment_results('custom_checks');
+        $this->assertNull(check_xmlrpc_usage($result));
+
+        $CFG->webserviceprotocols = 'rest';
+        $result = new environment_results('custom_checks');
+        $this->assertNull(check_xmlrpc_usage($result));
+    }
+
+    /**
+     * Test the check_xmlrpc_usage check when the XML-RPC web service method is set.
+     *
+     * @return void
+     */
+    public function test_check_xmlrpc_webservice_is_set(): void {
+        global $CFG;
+
+        $this->resetAfterTest();
+        $CFG->webserviceprotocols = 'xmlrpc,rest';
+
+        $result = new environment_results('custom_checks');
+        $this->assertInstanceOf(environment_results::class, check_xmlrpc_usage($result));
+        $this->assertEquals('xmlrpc_webservice_usage', $result->getInfo());
+        $this->assertFalse($result->getStatus());
+    }
+
+    /**
+     * Test the check_xmlrpc_usage check when the MNet is turned on but no host was set up.
+     *
+     * @return void
+     */
+    public function test_check_xmlrpc_mnet_host_is_not_set(): void {
+        global $CFG;
+
+        $this->resetAfterTest();
+        $CFG->mnet_dispatcher_mode = 'strict';
+
+        $result = new environment_results('custom_checks');
+        $this->assertNull(check_xmlrpc_usage($result));
+    }
+
+    /**
+     * Test the check_xmlrpc_usage check when the MNet is turned on and the host was set up.
+     *
+     * @return void
+     */
+    public function test_check_xmlrpc_mnet_host_is_set(): void {
+        global $CFG, $DB;
+
+        $this->resetAfterTest();
+        $CFG->mnet_dispatcher_mode = 'strict';
+
+        // Add a mnet host.
+        $mnethost = new stdClass();
+        $mnethost->name = 'A mnet host';
+        $mnethost->public_key = 'A random public key!';
+        $mnethost->id = $DB->insert_record('mnet_host', $mnethost);
+
+        $result = new environment_results('custom_checks');
+        $this->assertInstanceOf(environment_results::class, check_xmlrpc_usage($result));
+        $this->assertEquals('xmlrpc_mnet_usage', $result->getInfo());
+        $this->assertFalse($result->getStatus());
+    }
+
+    /**
+     * Test the check_xmlrpc_usage check when the MNet is turned on and the Mahara portfolios was set up.
+     *
+     * @return void
+     */
+    public function test_check_xmlrpc_mahara_portfolios_is_set(): void {
+        global $CFG;
+
+        $this->resetAfterTest();
+        $CFG->mnet_dispatcher_mode = 'strict';
+
+        // Enable the Mahara portfolios.
+        \core\plugininfo\portfolio::enable_plugin('mahara', 1);
+
+        $result = new environment_results('custom_checks');
+        $this->assertInstanceOf(environment_results::class, check_xmlrpc_usage($result));
+        $this->assertEquals('xmlrpc_mahara_usage', $result->getInfo());
+        $this->assertFalse($result->getStatus());
+    }
 }
diff --git a/lib/upgradelib.php b/lib/upgradelib.php
index f10b0a3590a..5528879f511 100644
--- a/lib/upgradelib.php
+++ b/lib/upgradelib.php
@@ -2732,3 +2732,55 @@ function check_admin_dir_usage(environment_results $result): ?environment_result
 
     return $result;
 }
+
+/**
+ * Check whether the XML-RPC protocol is enabled and warn if so.
+ *
+ * The XML-RPC protocol will be removed in a future version (4.1) as it is no longer supported by PHP.
+ *
+ * See MDL-70889 for further information.
+ *
+ * @param environment_results $result
+ * @return null|environment_results
+ */
+function check_xmlrpc_usage(environment_results $result): ?environment_results {
+    global $CFG;
+
+    // Checking Web Service protocols.
+    if (!empty($CFG->webserviceprotocols)) {
+        $plugins = array_flip(explode(',', $CFG->webserviceprotocols));
+        if (array_key_exists('xmlrpc', $plugins)) {
+            $result->setInfo('xmlrpc_webservice_usage');
+            $result->setFeedbackStr('xmlrpcwebserviceenabled');
+            return $result;
+        }
+    }
+
+    if (isset($CFG->mnet_dispatcher_mode) && $CFG->mnet_dispatcher_mode == 'strict') {
+        // Checking Mnet hosts.
+        $mnethosts = mnet_get_hosts();
+        if ($mnethosts) {
+            $actualhost = 0;
+            foreach ($mnethosts as $mnethost) {
+                if ($mnethost->id != $CFG->mnet_all_hosts_id) {
+                    $actualhost++;
+                }
+            }
+            if ($actualhost > 0) {
+                $result->setInfo('xmlrpc_mnet_usage');
+                $result->setFeedbackStr('xmlrpcmnetenabled');
+                return $result;
+            }
+        }
+
+        // Checking Mahara.
+        $portfolios = \core\plugininfo\portfolio::get_enabled_plugins();
+        if (array_key_exists('mahara', $portfolios)) {
+            $result->setInfo('xmlrpc_mahara_usage');
+            $result->setFeedbackStr('xmlrpcmaharaenabled');
+            return $result;
+        }
+    }
+
+    return null;
+}
diff --git a/mnet/environment.php b/mnet/environment.php
index 236e4b65ef7..ece0387311c 100644
--- a/mnet/environment.php
+++ b/mnet/environment.php
@@ -145,7 +145,10 @@ class mnet_environment {
         set_config('openssl', implode('@@@@@@@@', $this->keypair), 'mnet');
 
         $DB->update_record('mnet_host', $this);
-        error_log('New public key has been generated. It expires ' . date('Y/m/d h:i:s', $this->public_key_expires));
+        if (!PHPUNIT_TEST) {
+            // We don't want to output this log for PHPUnit since it will make the test to fail as risky.
+            error_log('New public key has been generated. It expires ' . date('Y/m/d h:i:s', $this->public_key_expires));
+        }
     }
 
     function get_private_key() {
diff --git a/mnet/lib.php b/mnet/lib.php
index e62fd865e94..f54f162a2fe 100644
--- a/mnet/lib.php
+++ b/mnet/lib.php
@@ -924,3 +924,15 @@ function mnet_strip_user($user, $fields) {
     }
     return $user;
 }
+
+/**
+ * Return the deprecation notice of the Mnet.
+ *
+ * @return \core\output\notification
+ */
+function mnet_get_deprecation_notice(): \core\output\notification {
+    $notice = new \core\output\notification(get_string('xmlrpcmnetenabled', 'admin'),
+        \core\output\notification::NOTIFY_WARNING);
+
+    return $notice;
+}
diff --git a/mnet/service/enrol/index.php b/mnet/service/enrol/index.php
index daa30ecc5b5..1938c6c6e7d 100644
--- a/mnet/service/enrol/index.php
+++ b/mnet/service/enrol/index.php
@@ -32,6 +32,7 @@ admin_externalpage_setup('mnetenrol');
 $service = mnetservice_enrol::get_instance();
 
 echo $OUTPUT->header();
+echo $OUTPUT->render(mnet_get_deprecation_notice());
 echo $OUTPUT->heading_with_help(get_string('clientname', 'mnetservice_enrol'), 'clientname', 'mnetservice_enrol');
 
 if (!$service->is_available()) {