.../media/css/filter.media_embed.css}              | 12 +++++---
 .../plugins/drupalmedia/ckeditor.drupalmedia.css   | 10 -------
 .../media/js/plugins/drupalmedia/plugin.es6.js     |  8 +++++
 .../modules/media/js/plugins/drupalmedia/plugin.js |  1 +
 core/modules/media/media.libraries.yml             |  6 ++++
 core/modules/media/media.routing.yml               |  2 +-
 .../src/Plugin/CKEditorPlugin/DrupalMedia.php      | 32 +++++---------------
 .../modules/media/src/Plugin/Filter/MediaEmbed.php | 12 ++++++--
 core/themes/classy/classy.libraries.yml            |  6 ----
 .../themes/stable/css/media/filter.media_embed.css | 34 ++++++++++++++++++++++
 core/themes/stable/stable.info.yml                 |  5 ++++
 11 files changed, 80 insertions(+), 48 deletions(-)

diff --git a/core/themes/classy/css/components/media-embed.css b/core/modules/media/css/filter.media_embed.css
similarity index 57%
rename from core/themes/classy/css/components/media-embed.css
rename to core/modules/media/css/filter.media_embed.css
index 3245be1914..c53ea56d9c 100644
--- a/core/themes/classy/css/components/media-embed.css
+++ b/core/modules/media/css/filter.media_embed.css
@@ -1,14 +1,18 @@
 /**
  * @file
- * Styles for media embeds.
+ * Media Embed filter: default styling for media embed errors.
  */
 
-.media-embed-error {
+/**
+ * The caption filter's styling overrides ours, so add a more specific selector to account for that.
+ */
+.media-embed-error,
+.caption > .media-embed-error {
   background-color: #ebebeb;
-  background-image: url(../../../../modules/media/images/icons/no-thumbnail.png);
+  background-image: url(../images/icons/no-thumbnail.png);
   background-repeat: no-repeat;
   background-position: center top;
-  padding: 100px 20px 20px 20px;
+  padding: 100px 20px 20px;
   background-size: 100px 100px;
   max-width: 200px;
   text-align: center;
diff --git a/core/modules/media/css/plugins/drupalmedia/ckeditor.drupalmedia.css b/core/modules/media/css/plugins/drupalmedia/ckeditor.drupalmedia.css
index 82bda3e66b..c0764a5ba1 100644
--- a/core/modules/media/css/plugins/drupalmedia/ckeditor.drupalmedia.css
+++ b/core/modules/media/css/plugins/drupalmedia/ckeditor.drupalmedia.css
@@ -64,13 +64,3 @@ drupal-media .caption {
   margin-bottom: 1em;
 }
 
-.media-embed-error {
-  background-color: #ebebeb;
-  background-image: url(../../../images/icons/no-thumbnail.png);
-  background-repeat: no-repeat;
-  background-position: center top;
-  padding: 100px 20px 20px;
-  background-size: 100px 100px;
-  max-width: 200px;
-  text-align: center;
-}
diff --git a/core/modules/media/js/plugins/drupalmedia/plugin.es6.js b/core/modules/media/js/plugins/drupalmedia/plugin.es6.js
index 5d6d33a10f..8e6c08ba75 100644
--- a/core/modules/media/js/plugins/drupalmedia/plugin.es6.js
+++ b/core/modules/media/js/plugins/drupalmedia/plugin.es6.js
@@ -177,8 +177,11 @@
             });
           }
 
+          // Allow entity_embed.editor.css to respond to changes (for example in alignment).
+          this.element.setAttributes(this.data.attributes);
           // Convert data-align attribute to class so we're not applying styles
           // to data attributes.
+          // @todo Consider removing this in https://www.drupal.org/project/drupal/issues/3072279
           if (this.data.attributes.hasOwnProperty('data-align')) {
             this.element
               .getParent()
@@ -271,6 +274,11 @@
         /**
          * Loads an media embed preview and runs a callback after insertion.
          *
+         * Note the absence of caching, that's because this uses a GET request (which is cacheable) and the server takes
+         * special care to make the responses privately cacheable (i.e. per session) in the browser.
+         *
+         * @see \Drupal\media\Controller\MediaFilterController::preview()
+         *
          * @param {function} callback
          *   A callback function that will be called after the preview has
          *   loaded. Receives the widget instance.
diff --git a/core/modules/media/js/plugins/drupalmedia/plugin.js b/core/modules/media/js/plugins/drupalmedia/plugin.js
index 2a135edcba..6290c9ecfd 100644
--- a/core/modules/media/js/plugins/drupalmedia/plugin.js
+++ b/core/modules/media/js/plugins/drupalmedia/plugin.js
@@ -139,6 +139,7 @@
             });
           }
 
+          this.element.setAttributes(this.data.attributes);
           if (this.data.attributes.hasOwnProperty('data-align')) {
             this.element.getParent().addClass('align-' + this.data.attributes['data-align']);
           }
diff --git a/core/modules/media/media.libraries.yml b/core/modules/media/media.libraries.yml
index 686e774521..d38fe369f5 100644
--- a/core/modules/media/media.libraries.yml
+++ b/core/modules/media/media.libraries.yml
@@ -31,3 +31,9 @@ filter.caption:
       css/filter.caption.css: {}
   dependencies:
     - filter/caption
+
+media_embed:
+  version: VERSION
+  css:
+    component:
+      css/filter.media_embed.css: {}
diff --git a/core/modules/media/media.routing.yml b/core/modules/media/media.routing.yml
index a93052883c..19dadf9e01 100644
--- a/core/modules/media/media.routing.yml
+++ b/core/modules/media/media.routing.yml
@@ -44,7 +44,7 @@ media.filter.preview:
   path: '/media/{filter_format}/preview'
   defaults:
     _controller: '\Drupal\media\Controller\MediaFilterController::preview'
-  methods:  [GET]
+  methods: [GET]
   requirements:
     _entity_access: 'filter_format.use'
     _custom_access: '\Drupal\media\Controller\MediaFilterController::formatUsesMediaEmbedFilter'
diff --git a/core/modules/media/src/Plugin/CKEditorPlugin/DrupalMedia.php b/core/modules/media/src/Plugin/CKEditorPlugin/DrupalMedia.php
index c83030f286..35717d5a76 100644
--- a/core/modules/media/src/Plugin/CKEditorPlugin/DrupalMedia.php
+++ b/core/modules/media/src/Plugin/CKEditorPlugin/DrupalMedia.php
@@ -4,7 +4,6 @@
 
 use Drupal\ckeditor\CKEditorPluginContextualInterface;
 use Drupal\ckeditor\CKEditorPluginCssInterface;
-use Drupal\Core\Asset\LibraryDiscoveryInterface;
 use Drupal\Core\Extension\ModuleExtensionList;
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -33,13 +32,6 @@ class DrupalMedia extends PluginBase implements ContainerFactoryPluginInterface,
    */
   protected $moduleExtensionList;
 
-  /**
-   * The library discovery service.
-   *
-   * @var \Drupal\Core\Asset\LibraryDiscoveryInterface
-   */
-  protected $libraryDiscovery;
-
   /**
    * Constructs a new DrupalMedia plugin object.
    *
@@ -51,13 +43,10 @@ class DrupalMedia extends PluginBase implements ContainerFactoryPluginInterface,
    *   The plugin implementation definition.
    * @param \Drupal\Core\Extension\ModuleExtensionList $extension_list_module
    *   The module extension list.
-   * @param \Drupal\Core\Asset\LibraryDiscoveryInterface $library_discovery
-   *   The library discovery service.
    */
-  public function __construct(array $configuration, $plugin_id, $plugin_definition, ModuleExtensionList $extension_list_module, LibraryDiscoveryInterface $library_discovery) {
+  public function __construct(array $configuration, $plugin_id, $plugin_definition, ModuleExtensionList $extension_list_module) {
     parent::__construct($configuration, $plugin_id, $plugin_definition);
     $this->moduleExtensionList = $extension_list_module;
-    $this->libraryDiscovery = $library_discovery;
   }
 
   /**
@@ -68,8 +57,7 @@ public static function create(ContainerInterface $container, array $configuratio
       $configuration,
       $plugin_id,
       $plugin_definition,
-      $container->get('extension.list.module'),
-      $container->get('library.discovery')
+      $container->get('extension.list.module')
     );
   }
 
@@ -92,6 +80,8 @@ public function getDependencies(Editor $editor) {
    */
   public function getLibraries(Editor $editor) {
     return [
+      'core/jquery',
+      'core/drupal',
       'core/drupal.ajax',
     ];
   }
@@ -127,20 +117,14 @@ public function isEnabled(Editor $editor) {
   /**
    * {@inheritdoc}
    *
-   * @todo Generalize this in https://www.drupal.org/project/drupal/issues/3072063
+   * @todo Improve this in https://www.drupal.org/project/drupal/issues/3072063
    */
   public function getCssFiles(Editor $editor) {
-    $files = [
+    return [
+      $this->moduleExtensionList->getPath('media') . '/css/filter.media_embed.css',
       $this->moduleExtensionList->getPath('media') . '/css/plugins/drupalmedia/ckeditor.drupalmedia.css',
+      $this->moduleExtensionList->getPath('system') . '/css/components/hidden.module.css',
     ];
-    // Get current version of 'hidden.module.css', taking into account module
-    // and theme overrides.
-    $library = $this->libraryDiscovery->getLibraryByName('system', 'base');
-    foreach (preg_grep('/hidden\.module\.css$/', array_column($library['css'], 'data')) as $file) {
-      $files[] = $file;
-      break;
-    }
-    return $files;
   }
 
 }
diff --git a/core/modules/media/src/Plugin/Filter/MediaEmbed.php b/core/modules/media/src/Plugin/Filter/MediaEmbed.php
index ca9a034118..3145258cba 100644
--- a/core/modules/media/src/Plugin/Filter/MediaEmbed.php
+++ b/core/modules/media/src/Plugin/Filter/MediaEmbed.php
@@ -218,6 +218,11 @@ protected function renderMissingMediaIndicator() {
       '#type' => 'html_tag',
       '#tag' => 'div',
       '#value' => $this->t('The referenced media source is missing and needs to be re-embedded.'),
+      '#attached' => [
+        'library' => [
+          'media/media_embed',
+        ],
+      ],
       '#attributes' => [
         'class' => [
           'media-embed-error',
@@ -279,9 +284,10 @@ public function process($text, $langcode) {
       // at least the caption and visual structure won't get lost.
       foreach ($node->attributes as $attribute) {
         if ($attribute->nodeName == 'class') {
-          // We don't want to overwrite existing class of the embed (or the
-          // missing media indicator), but we need to merge in classes such as
-          // those added by filter_align in order for those filters to function
+          // We don't want to overwrite the existing CSS class of the embedded
+          // media (or if the media entity can't be loaded, the missing media
+          // indicator). But, we need to merge in CSS classes added by other
+          // filters, such as filter_align, in order for those filters to work
           // properly.
           $build['#attributes']['class'] = array_unique(array_merge($build['#attributes']['class'], explode(' ', $attribute->nodeValue)));
         }
diff --git a/core/themes/classy/classy.libraries.yml b/core/themes/classy/classy.libraries.yml
index 4597badff5..f970f86b15 100644
--- a/core/themes/classy/classy.libraries.yml
+++ b/core/themes/classy/classy.libraries.yml
@@ -68,12 +68,6 @@ indented:
     component:
       css/components/indented.css: {}
 
-media_embed_error:
-  version: VERSION
-  css:
-    component:
-      css/components/media-embed.css: { weight: -10 }
-
 messages:
   version: VERSION
   css:
diff --git a/core/themes/stable/css/media/filter.media_embed.css b/core/themes/stable/css/media/filter.media_embed.css
new file mode 100644
index 0000000000..9842664516
--- /dev/null
+++ b/core/themes/stable/css/media/filter.media_embed.css
@@ -0,0 +1,34 @@
+/**
+ * @file
+ * Media Embed filter: default styling for media embed errors.
+ */
+
+/**
+ * The caption filter's styling overrides ours, so add a more specific selector to account for that.
+ */
+.media-embed-error,
+.caption > .media-embed-error {
+  background-color: #ebebeb;
+  background-image: url(../../images/media/icons/no-thumbnail.png);
+  background-repeat: no-repeat;
+  background-position: center top;
+  padding: 100px 20px 20px;
+  background-size: 100px 100px;
+  max-width: 200px;
+  text-align: center;
+}
+
+.media-embed-error.align-left {
+  margin-right: 1em;
+  margin-bottom: 1em;
+}
+
+.media-embed-error.align-right  {
+  margin-left: 1em;
+  margin-bottom: 1em;
+}
+
+.media-embed-error.align-center  {
+  margin-top: 1em;
+  margin-bottom: 1em;
+}
diff --git a/core/themes/stable/stable.info.yml b/core/themes/stable/stable.info.yml
index 91deed83a2..2d2aa148c5 100644
--- a/core/themes/stable/stable.info.yml
+++ b/core/themes/stable/stable.info.yml
@@ -158,6 +158,11 @@ libraries-override:
       component:
         css/oembed.frame.css: css/media/oembed.frame.css
 
+  media/media_embed:
+    css:
+      component:
+        css/filter.media_embed.css: css/media/filter.media_embed.css
+
   menu_ui/drupal.menu_ui.adminforms:
     css:
       theme: