diff --git a/core/modules/ckeditor/ckeditor.admin.inc b/core/modules/ckeditor/ckeditor.admin.inc
index 4ee12bb..21be21d 100644
--- a/core/modules/ckeditor/ckeditor.admin.inc
+++ b/core/modules/ckeditor/ckeditor.admin.inc
@@ -7,7 +7,6 @@
 
 use Drupal\Component\Utility\Html;
 use Drupal\Core\Template\Attribute;
-use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Language\LanguageInterface;
 
 /**
@@ -66,10 +65,10 @@ function template_preprocess_ckeditor_settings_toolbar(&$variables) {
   $build_button_item = function($button, $rtl) {
     // Value of the button item.
     if (isset($button['image_alternative' . $rtl])) {
-      $value = SafeMarkup::set($button['image_alternative' . $rtl]);
+      $value = $button['image_alternative' . $rtl];
     }
     elseif (isset($button['image_alternative'])) {
-      $value = SafeMarkup::set($button['image_alternative']);
+      $value = $button['image_alternative'];
     }
     elseif (isset($button['image'])) {
       $value = array(
diff --git a/core/modules/ckeditor/src/Plugin/CKEditorPlugin/Internal.php b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/Internal.php
index c405c7f..2385511 100644
--- a/core/modules/ckeditor/src/Plugin/CKEditorPlugin/Internal.php
+++ b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/Internal.php
@@ -127,7 +127,18 @@ public function getConfig(Editor $editor) {
    */
   public function getButtons() {
     $button = function($name, $direction = 'ltr') {
-      return '<a href="#" class="cke-icon-only cke_' . $direction . '" role="button" title="' . $name . '" aria-label="' . $name . '"><span class="cke_button_icon cke_button__' . str_replace(' ', '', $name) . '_icon">' . $name . '</span></a>';
+      // In the markup below, we mostly use the name (which may include spaces),
+      // but in one spot we use it as a CSS class, so strip spaces.
+      $class_name = str_replace(' ', '', $name);
+      return [
+        '#type' => 'inline_template',
+        '#template' => '<a href="#" class="cke-icon-only cke_{{ direction }}" role="button" title="{{ name }}" aria-label="{{ name }}"><span class="cke_button_icon cke_button__{{ classname }}_icon">{{ name }}</span></a>',
+        '#context' => [
+          'direction' => $direction,
+          'name' => $name,
+          'classname' => $class_name,
+        ],
+      ];
     };
 
     return array(
@@ -256,7 +267,13 @@ public function getButtons() {
       ),
       'Format' => array(
         'label' => t('HTML block format'),
-        'image_alternative' => '<a href="#" role="button" aria-label="' . t('Format') . '"><span class="ckeditor-button-dropdown">' . t('Format') . '<span class="ckeditor-button-arrow"></span></span></a>',
+        'image_alternative' => [
+          '#type' => 'inline_template',
+          '#template' => '<a href="#" role="button" aria-label="{{ format_text }}"><span class="ckeditor-button-dropdown">{{ format_text }}<span class="ckeditor-button-arrow"></span></span></a>',
+          '#context' => [
+            'format_text' => t('Format'),
+          ],
+        ],
       ),
       // "table" plugin.
       'Table' => array(
@@ -282,7 +299,13 @@ public function getButtons() {
       // No plugin, separator "button" for toolbar builder UI use only.
       '-' => array(
         'label' => t('Separator'),
-        'image_alternative' => '<a href="#" role="button" aria-label="' . t('Button separator') . '" class="ckeditor-separator"></a>',
+        'image_alternative' => [
+          '#type' => 'inline_template',
+          '#template' => '<a href="#" role="button" aria-label="{{ button_separator_text }}" class="ckeditor-separator"></a>',
+          '#context' => [
+            'button_separator_text' => t('Button separator'),
+          ],
+        ],
         'attributes' => array(
           'class' => array('ckeditor-button-separator'),
           'data-drupal-ckeditor-type' => 'separator',
diff --git a/core/modules/ckeditor/src/Plugin/CKEditorPlugin/StylesCombo.php b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/StylesCombo.php
index d569930..d3eb49f 100644
--- a/core/modules/ckeditor/src/Plugin/CKEditorPlugin/StylesCombo.php
+++ b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/StylesCombo.php
@@ -59,7 +59,13 @@ public function getButtons() {
     return array(
       'Styles' => array(
         'label' => t('Font style'),
-        'image_alternative' => '<a href="#" role="button" aria-label="' . t('Styles') . '"><span class="ckeditor-button-dropdown">' . t('Styles') . '<span class="ckeditor-button-arrow"></span></span></a>',
+        'image_alternative' => [
+          '#type' => 'inline_template',
+          '#template' => '<a href="#" role="button" aria-label="{{ styles_text }}"><span class="ckeditor-button-dropdown">{{ styles_text }}<span class="ckeditor-button-arrow"></span></span></a>',
+          '#context' => [
+            'styles_text' => t('Styles'),
+          ],
+        ],
       ),
     );
   }
diff --git a/core/modules/ckeditor/src/Tests/CKEditorAdminTest.php b/core/modules/ckeditor/src/Tests/CKEditorAdminTest.php
index 3ce8271..ca1954f 100644
--- a/core/modules/ckeditor/src/Tests/CKEditorAdminTest.php
+++ b/core/modules/ckeditor/src/Tests/CKEditorAdminTest.php
@@ -7,6 +7,7 @@
 
 namespace Drupal\ckeditor\Tests;
 
+use Drupal\Component\Serialization\Json;
 use Drupal\editor\Entity\Editor;
 use Drupal\filter\FilterFormatInterface;
 use Drupal\simpletest\WebTestBase;
@@ -176,6 +177,22 @@ function testExistingFormat() {
     $this->assertTrue($editor instanceof Editor, 'An Editor config entity exists.');
     $this->assertIdentical($expected_settings, $editor->getSettings(), 'The Editor config entity has the correct settings.');
 
+    // Check that the markup we're setting for the toolbar buttons (actually in
+    // JavaScript's drupalSettings, and Unicode-escaped) is correctly rendered.
+    $this->drupalGet('admin/config/content/formats/manage/filtered_html');
+    // Create function to encode HTML as we expect it in drupalSettings.
+    $json_encode = function($html) {
+      return trim(Json::encode($html), '"');
+    };
+    // Check the Button separator.
+    $this->assertRaw($json_encode('<li data-drupal-ckeditor-button-name="-" class="ckeditor-button-separator ckeditor-multiple-button" data-drupal-ckeditor-type="separator"><a href="#" role="button" aria-label="Button separator" class="ckeditor-separator"></a></li>'));
+    // Check the Format dropdown.
+    $this->assertRaw($json_encode('<li data-drupal-ckeditor-button-name="Format" class="ckeditor-button"><a href="#" role="button" aria-label="Format"><span class="ckeditor-button-dropdown">Format<span class="ckeditor-button-arrow"></span></span></a></li>'));
+    // Check the Styles dropdown.
+    $this->assertRaw($json_encode('<li data-drupal-ckeditor-button-name="Styles" class="ckeditor-button"><a href="#" role="button" aria-label="Styles"><span class="ckeditor-button-dropdown">Styles<span class="ckeditor-button-arrow"></span></span></a></li>'));
+    // Check strikethrough.
+    $this->assertRaw($json_encode('<li data-drupal-ckeditor-button-name="Strike" class="ckeditor-button"><a href="#" class="cke-icon-only cke_ltr" role="button" title="strike" aria-label="strike"><span class="cke_button_icon cke_button__strike_icon">strike</span></a></li>'));
+
     // Now enable the ckeditor_test module, which provides one configurable
     // CKEditor plugin — this should not affect the Editor config entity.
     \Drupal::service('module_installer')->install(array('ckeditor_test'));