diff --git a/lib/h5p/h5p-metadata.class.php b/lib/h5p/h5p-metadata.class.php
index 572cfd0324d..2154f27a71e 100644
--- a/lib/h5p/h5p-metadata.class.php
+++ b/lib/h5p/h5p-metadata.class.php
@@ -107,7 +107,7 @@ abstract class H5PMetadata {
       switch ($config['type']) {
         case 'text':
           if ($value !== null && strlen($value) > $config['maxLength']) {
-            $value = mb_substr($value, 0, $config['maxLength']);
+            $value = \core_text::substr($value, 0, $config['maxLength']);
           }
           $types[] = '%s';
           break;
diff --git a/lib/h5p/h5p.classes.php b/lib/h5p/h5p.classes.php
index 7176ad00431..a624cf8c49a 100644
--- a/lib/h5p/h5p.classes.php
+++ b/lib/h5p/h5p.classes.php
@@ -758,11 +758,14 @@ class H5PValidator {
       unlink($tmpPath);
       return FALSE;
     }
+    // Moodle: the extension mbstring is optional.
+    /*
     if (!extension_loaded('mbstring')) {
       $this->h5pF->setErrorMessage($this->h5pF->t('The mbstring PHP extension is not loaded. H5P need this to function properly'), 'mbstring-unsupported');
       unlink($tmpPath);
       return FALSE;
     }
+    */
 
     // Create a temporary dir to extract package in.
     $tmpDir = $this->h5pF->getUploadedH5pFolderPath();
@@ -809,7 +812,7 @@ class H5PValidator {
       }
       $totalSize += $fileStat['size'];
 
-      $fileName = mb_strtolower($fileStat['name']);
+      $fileName = \core_text::strtolower($fileStat['name']);
       if (preg_match('/(^[\._]|\/[\._])/', $fileName) !== 0) {
         continue; // Skip any file or folder starting with a . or _
       }
@@ -2432,7 +2435,7 @@ class H5PCore {
     // Using content dependencies
     foreach ($dependencies as $dependency) {
       if (isset($dependency['path']) === FALSE) {
-        $dependency['path'] = 'libraries/' . H5PCore::libraryToString($dependency, TRUE);
+        $dependency['path'] = $this->getDependencyPath($dependency);
         $dependency['preloadedJs'] = explode(',', $dependency['preloadedJs']);
         $dependency['preloadedCss'] = explode(',', $dependency['preloadedCss']);
       }
@@ -2452,6 +2455,16 @@ class H5PCore {
     return $files;
   }
 
+  /**
+   * Get the path to the dependency.
+   *
+   * @param stdClass $dependency
+   * @return string
+   */
+  protected function getDependencyPath(array $dependency): string {
+    return H5PCore::libraryToString($dependency, TRUE);
+  }
+
   private static function getDependenciesHash(&$dependencies) {
     // Build hash of dependencies
     $toHash = array();
@@ -3303,12 +3316,15 @@ class H5PCore {
       $setup->disable_hub = TRUE;
     }
 
+    // Moodle: the extension mbstring is optional.
+    /*
     if (!extension_loaded('mbstring')) {
       $setup->errors[] = $this->h5pF->t(
         'The mbstring PHP extension is not loaded. H5P needs this to function properly'
       );
       $setup->disable_hub = TRUE;
     }
+    */
 
     // Check php version >= 5.2
     $php_version = explode('.', phpversion());
@@ -3656,12 +3672,13 @@ class H5PContentValidator {
 
     // Check if string is within allowed length
     if (isset($semantics->maxLength)) {
+      // Moodle: the extension mbstring is optional.
+      /*
       if (!extension_loaded('mbstring')) {
         $this->h5pF->setErrorMessage($this->h5pF->t('The mbstring PHP extension is not loaded. H5P need this to function properly'), 'mbstring-unsupported');
       }
-      else {
-        $text = mb_substr($text, 0, $semantics->maxLength);
-      }
+      */
+      $text = \core_text::substr($text, 0, $semantics->maxLength);
     }
 
     // Check if string is according to optional regexp in semantics
@@ -3711,11 +3728,14 @@ class H5PContentValidator {
         // file name, 2. testing against a returned error array that could
         // never be more than 1 element long anyway, 3. recreating the regex
         // for every file.
+        // Moodle: the extension mbstring is optional.
+        /*
         if (!extension_loaded('mbstring')) {
           $this->h5pF->setErrorMessage($this->h5pF->t('The mbstring PHP extension is not loaded. H5P need this to function properly'), 'mbstring-unsupported');
           $valid = FALSE;
         }
-        else if (!preg_match($wl_regex, mb_strtolower($file))) {
+        */
+        if (!preg_match($wl_regex, \core_text::strtolower($file))) {
           $this->h5pF->setErrorMessage($this->h5pF->t('File "%filename" not allowed. Only files with the following extensions are allowed: %files-allowed.', array('%filename' => $file, '%files-allowed' => $whitelist)), 'not-in-whitelist');
           $valid = FALSE;
         }
diff --git a/lib/h5p/readme_moodle.txt b/lib/h5p/readme_moodle.txt
index ed3ce037205..2eb2896e40e 100644
--- a/lib/h5p/readme_moodle.txt
+++ b/lib/h5p/readme_moodle.txt
@@ -14,18 +14,34 @@ Removed:
 Added:
  * readme_moodle.txt
 
-Downloaded version: 1.23.1 release
+Downloaded version: 1.24 release
+
 
 === 3.8 ===
-* In order to allow the dependency path to be overridden by child H5PCore classes, a couple of minor changes have been added to the
+1. In order to allow the dependency path to be overridden by child H5PCore classes, a couple of minor changes have been added to the
 h5p.classes.php file:
     - Into the getDependenciesFiles method, the line 2435:
         $dependency['path'] = 'libraries/' . H5PCore::libraryToString($dependency, TRUE);
 
       has been changed to:
-      	$dependency['path'] = $this->getDependencyPath($dependency);
+        $dependency['path'] = $this->getDependencyPath($dependency);
 
      - The method getDependencyPath has been added (line 2455). It might be rewritten by child classes.
 A PR has been sent to the H5P library with these changes:
 https://github.com/h5p/h5p-php-library/compare/master...andrewnicols:libraryPathSubclass
-Hopefully, when upgrading, these patch won't be needed because it will be included in the H5P library by default.
\ No newline at end of file
+Hopefully, when upgrading, these patch won't be needed because it will be included in the H5P library by default.
+
+
+2. As the mbstring extension is optional in Moodle, the following changes have been hardcoded to the library:
+2.1. Comment the following methods in h5p.classes.php file where the extension_loaded('mbstring') is called:
+    * isValidPackage
+    * checkSetupErrorMessage
+    * validateText
+    * validateContentFiles
+
+2.2. Change all the mb_uses straight to the core_text() alternatives. Version 1.24 has 3 ocurrences in h5p.classes.php
+and 1 ocurrence in h5p-metadata.class.php.
+
+
+The point 2 from above won't be needed once the mbstring extension becomes mandatory in Moodle. A request has been
+sent to MDL-65809.
\ No newline at end of file
diff --git a/lib/thirdpartylibs.xml b/lib/thirdpartylibs.xml
index b901656ca51..89c1b67f1f4 100644
--- a/lib/thirdpartylibs.xml
+++ b/lib/thirdpartylibs.xml
@@ -318,6 +318,6 @@
     <location>h5p</location>
     <name>h5p-php-library</name>
     <license>GPL-3.0</license>
-    <version>1.23.1</version>
+    <version>1.24</version>
   </library>
 </libraries>