diff --git a/modules/media/js/plugins/drupalmedia/plugin.es6.js b/modules/media/js/plugins/drupalmedia/plugin.es6.js
index ef7ea3f9b58..66152eb481b 100644
--- a/modules/media/js/plugins/drupalmedia/plugin.es6.js
+++ b/modules/media/js/plugins/drupalmedia/plugin.es6.js
@@ -472,6 +472,9 @@
               uuid: this.data.attributes['data-entity-uuid'],
             },
             dataType: 'html',
+            headers: {
+              'X-Drupal-MediaPreview-CSRF-Token': editor.config.drupalMedia_previewCsrfToken,
+            },
             success: (previewHtml, textStatus, jqXhr) => {
               this.element.setHtml(previewHtml);
               this.setData(
diff --git a/modules/media/js/plugins/drupalmedia/plugin.js b/modules/media/js/plugins/drupalmedia/plugin.js
index 7061bf81447..9f323d37e92 100644
--- a/modules/media/js/plugins/drupalmedia/plugin.js
+++ b/modules/media/js/plugins/drupalmedia/plugin.js
@@ -314,6 +314,9 @@
               uuid: this.data.attributes['data-entity-uuid']
             },
             dataType: 'html',
+            headers: {
+              'X-Drupal-MediaPreview-CSRF-Token': editor.config.drupalMedia_previewCsrfToken
+            },
             success: function success(previewHtml, textStatus, jqXhr) {
               _this3.element.setHtml(previewHtml);
               _this3.setData('label', jqXhr.getResponseHeader('Drupal-Media-Label'));
diff --git a/modules/media/src/Controller/MediaFilterController.php b/modules/media/src/Controller/MediaFilterController.php
index 4b9ea6bfefe..06e11a1848b 100644
--- a/modules/media/src/Controller/MediaFilterController.php
+++ b/modules/media/src/Controller/MediaFilterController.php
@@ -7,10 +7,12 @@
 use Drupal\Core\Entity\ContentEntityStorageInterface;
 use Drupal\Core\Entity\EntityRepositoryInterface;
 use Drupal\Core\Render\RendererInterface;
+use Drupal\Core\Session\AccountInterface;
 use Drupal\filter\FilterFormatInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\HttpKernel\Exception\AccessDeniedHttpException;
 use Symfony\Component\HttpKernel\Exception\NotFoundHttpException;
 
 /**
@@ -93,6 +95,8 @@ public static function create(ContainerInterface $container) {
    * @see \Drupal\editor\EditorController::getUntransformedText
    */
   public function preview(Request $request, FilterFormatInterface $filter_format) {
+    self::checkCsrf($request, \Drupal::currentUser());
+
     $text = $request->query->get('text');
     $uuid = $request->query->get('uuid');
     if ($text == '' || $uuid == '') {
@@ -140,4 +144,30 @@ public static function formatUsesMediaEmbedFilter(FilterFormatInterface $filter_
       ->addCacheableDependency($filter_format);
   }
 
+  /**
+   * Throws an AccessDeniedHttpException if the request fails CSRF validation.
+   *
+   * This is used instead of \Drupal\Core\Access\CsrfAccessCheck, in order to
+   * allow access for anonymous users.
+   *
+   * @todo Refactor this to an access checker.
+   */
+  private static function checkCsrf(Request $request, AccountInterface $account) {
+    $header = 'X-Drupal-MediaPreview-CSRF-Token';
+
+    if (!$request->headers->has($header)) {
+      throw new AccessDeniedHttpException();
+    }
+    if ($account->isAnonymous()) {
+      // For anonymous users, just the presence of the custom header is
+      // sufficient protection.
+      return;
+    }
+    // For authenticated users, validate the token value.
+    $token = $request->headers->get($header);
+    if (!\Drupal::csrfToken()->validate($token, $header)) {
+      throw new AccessDeniedHttpException();
+    }
+  }
+
 }
diff --git a/modules/media/src/Plugin/CKEditorPlugin/DrupalMedia.php b/modules/media/src/Plugin/CKEditorPlugin/DrupalMedia.php
index c3aff900d65..d475f1ab9c7 100644
--- a/modules/media/src/Plugin/CKEditorPlugin/DrupalMedia.php
+++ b/modules/media/src/Plugin/CKEditorPlugin/DrupalMedia.php
@@ -98,7 +98,9 @@ public function getFile() {
    * {@inheritdoc}
    */
   public function getConfig(Editor $editor) {
-    return [];
+    return [
+      'drupalMedia_previewCsrfToken' => \Drupal::csrfToken()->get('X-Drupal-MediaPreview-CSRF-Token'),
+    ];
   }
 
   /**
diff --git a/modules/media/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php b/modules/media/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
index 3909303322d..3074efcfb37 100644
--- a/modules/media/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
+++ b/modules/media/tests/src/FunctionalJavascript/CKEditorIntegrationTest.php
@@ -3,7 +3,6 @@
 namespace Drupal\Tests\media\FunctionalJavascript;
 
 use Drupal\Component\Utility\Html;
-use Drupal\Core\Url;
 use Drupal\editor\Entity\Editor;
 use Drupal\field\Entity\FieldConfig;
 use Drupal\file\Entity\File;
@@ -1027,14 +1026,13 @@ public function linkabilityProvider() {
    * @dataProvider previewAccessProvider
    */
   public function testEmbedPreviewAccess($media_embed_enabled, $can_use_format) {
-    $format = FilterFormat::create([
-      'format' => $this->randomMachineName(),
-      'name' => $this->randomString(),
-      'filters' => [
-        'filter_align' => ['status' => TRUE],
-        'filter_caption' => ['status' => TRUE],
-        'media_embed' => ['status' => $media_embed_enabled],
-      ],
+    // Reconfigure the host entity's text format to suit our needs.
+    /** @var \Drupal\filter\FilterFormatInterface $format */
+    $format = FilterFormat::load($this->host->body->format);
+    $format->set('filters', [
+      'filter_align' => ['status' => TRUE],
+      'filter_caption' => ['status' => TRUE],
+      'media_embed' => ['status' => $media_embed_enabled],
     ]);
     $format->save();
 
@@ -1045,24 +1043,23 @@ public function testEmbedPreviewAccess($media_embed_enabled, $can_use_format) {
       $permissions[] = $format->getPermissionName();
     }
     $this->drupalLogin($this->drupalCreateUser($permissions));
-
-    $text = '<drupal-media data-caption="baz" data-entity-type="media" data-entity-uuid="' . $this->media->uuid() . '"></drupal-media>';
-    $route_parameters = ['filter_format' => $format->id()];
-    $options = [
-      'query' => [
-        'text' => $text,
-        'uuid' => $this->media->uuid(),
-      ],
-    ];
-    $this->drupalGet(Url::fromRoute('media.filter.preview', $route_parameters, $options));
+    $this->drupalGet($this->host->toUrl('edit-form'));
 
     $assert_session = $this->assertSession();
-    if ($media_embed_enabled && $can_use_format) {
-      $assert_session->elementExists('css', 'img');
-      $assert_session->responseContains('baz');
+    if ($can_use_format) {
+      $this->waitForEditor();
+      $this->assignNameToCkeditorIframe();
+      $this->getSession()->switchToIFrame('ckeditor');
+      if ($media_embed_enabled) {
+        $this->assertNotEmpty($assert_session->waitForElementVisible('css', 'article.media'));
+      }
+      else {
+        $assert_session->assertWaitOnAjaxRequest();
+        $assert_session->elementNotExists('css', 'article.media');
+      }
     }
     else {
-      $assert_session->responseContains('You are not authorized to access this page.');
+      $assert_session->pageTextContains('This field has been disabled because you do not have sufficient permissions to edit it.');
     }
   }