.../ckeditor/Plugin/CKEditorPlugin/Internal.php    |  6 ++++
 core/modules/comment/comment.module                |  8 +----
 .../editor/Plugin/Filter/EditorFileReference.php   | 12 ++++++--
 .../editor/Tests/EditorFileReferenceFilterTest.php | 35 +++++++++-------------
 .../lib/Drupal/system/Tests/Common/RenderTest.php  |  8 ++---
 5 files changed, 34 insertions(+), 35 deletions(-)

diff --git a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/Internal.php b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/Internal.php
index 186964b..c0faa78 100644
--- a/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/Internal.php
+++ b/core/modules/ckeditor/lib/Drupal/ckeditor/Plugin/CKEditorPlugin/Internal.php
@@ -252,6 +252,12 @@ public function getButtons() {
    *   An array containing the "format_tags" configuration.
    */
   protected function generateFormatTagsSetting(Editor $editor) {
+    // When no text format is associated yet, assume no tag is allowed.
+    // @see \Drupal\Editor\EditorInterface::hasAssociatedFilterFormat()
+    if (!$editor->hasAssociatedFilterFormat()) {
+      return array();
+    }
+
     $format = $editor->getFilterFormat();
     $cid = 'ckeditor_internal_format_tags:' . $format->id();
 
diff --git a/core/modules/comment/comment.module b/core/modules/comment/comment.module
index fea8dee..be95620 100644
--- a/core/modules/comment/comment.module
+++ b/core/modules/comment/comment.module
@@ -13,7 +13,6 @@
 use Drupal\comment\CommentInterface;
 use Drupal\comment\Entity\Comment;
 use Drupal\comment\Plugin\Field\FieldType\CommentItemInterface;
-use Drupal\Component\Utility\String;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\entity\Entity\EntityViewDisplay;
 use Drupal\Core\Entity\Display\EntityViewDisplayInterface;
@@ -23,7 +22,6 @@
 use Drupal\field\FieldInstanceConfigInterface;
 use Drupal\field\FieldConfigInterface;
 use Drupal\file\FileInterface;
-use Drupal\filter\FilterProcessResult;
 use Drupal\user\EntityOwnerInterface;
 use Drupal\node\NodeInterface;
 use Symfony\Component\HttpFoundation\Request;
@@ -1361,11 +1359,7 @@ function template_preprocess_comment(&$variables) {
   }
 
   if (isset($variables['elements']['signature'])) {
-    $signature = $variables['elements']['signature']['#markup'];
-    if (!$signature instanceof FilterProcessResult) {
-      $signature = String::checkPlain($signature);
-    }
-    $variables['signature'] = (string) $signature;
+    $variables['signature'] = $variables['elements']['signature']['#markup'];
     unset($variables['elements']['signature']);
   }
   else {
diff --git a/core/modules/editor/lib/Drupal/editor/Plugin/Filter/EditorFileReference.php b/core/modules/editor/lib/Drupal/editor/Plugin/Filter/EditorFileReference.php
index 6306f27..5ebb267 100644
--- a/core/modules/editor/lib/Drupal/editor/Plugin/Filter/EditorFileReference.php
+++ b/core/modules/editor/lib/Drupal/editor/Plugin/Filter/EditorFileReference.php
@@ -36,11 +36,17 @@ public function process($text, $langcode) {
       $all_file_cache_tags = array();
       $dom = Html::load($text);
       $xpath = new \DOMXPath($dom);
+      $processed_uuids = array();
       foreach ($xpath->query('//*[@data-editor-file-uuid]') as $node) {
         $uuid = $node->getAttribute('data-editor-file-uuid');
-        $file = entity_load_by_uuid('file', $uuid);
-        if ($file) {
-          $all_file_cache_tags[] = $file->getCacheTag();
+        // Only process the first occurrence of each file UUID.
+        if (!isset($processed_uuids[$uuid])) {
+          $processed_uuids[$uuid] = TRUE;
+
+          $file = entity_load_by_uuid('file', $uuid);
+          if ($file) {
+            $all_file_cache_tags[] = $file->getCacheTag();
+          }
         }
       }
       $result->setCacheTags(NestedArray::mergeDeepArray($all_file_cache_tags));
diff --git a/core/modules/editor/lib/Drupal/editor/Tests/EditorFileReferenceFilterTest.php b/core/modules/editor/lib/Drupal/editor/Tests/EditorFileReferenceFilterTest.php
index 4961126..d0bfbb5 100644
--- a/core/modules/editor/lib/Drupal/editor/Tests/EditorFileReferenceFilterTest.php
+++ b/core/modules/editor/lib/Drupal/editor/Tests/EditorFileReferenceFilterTest.php
@@ -58,14 +58,7 @@ function testEditorFileReferenceFilter() {
     $filter = $this->filters['editor_file_reference'];
 
     $test = function($input) use ($filter) {
-      $filtered = $filter->process($input, 'und');
-      if (is_string($filtered)) {
-        return $filtered;
-      }
-      else {
-        drupal_render($filtered);
-        return $filtered;
-      }
+      return $filter->process($input, 'und');
     };
 
     file_put_contents('public://llama.jpg', $this->randomName());
@@ -83,45 +76,45 @@ function testEditorFileReferenceFilter() {
     $this->pass('No data-editor-file-uuid attribute.');
     $input = '<img src="llama.jpg" />';
     $output = $test($input);
-    $this->assertIdentical($input, $output);
+    $this->assertIdentical($input, $output->getProcessedText());
 
     $this->pass('One data-editor-file-uuid attribute.');
     $input = '<img src="llama.jpg" data-editor-file-uuid="' . $uuid . '" />';
     $output = $test($input);
-    $this->assertIdentical($input, $output['#markup']);
-    $this->assertEqual(array('file' => array($id => $id)), $output['#cache']['tags']);
+    $this->assertIdentical($input, $output->getProcessedText());
+    $this->assertEqual(array('file' => array($id)), $output->getCacheTags());
 
     $this->pass('One data-editor-file-uuid attribute with odd capitalization.');
     $input = '<img src="llama.jpg" DATA-editor-file-UUID =   "' . $uuid . '" />';
     $output = $test($input);
-    $this->assertIdentical($input, $output['#markup']);
-    $this->assertEqual(array('file' => array($id => $id)), $output['#cache']['tags']);
+    $this->assertIdentical($input, $output->getProcessedText());
+    $this->assertEqual(array('file' => array($id)), $output->getCacheTags());
 
     $this->pass('One data-editor-file-uuid attribute on a non-image tag.');
     $input = '<video src="llama.jpg" data-editor-file-uuid="' . $uuid . '" />';
     $output = $test($input);
-    $this->assertIdentical($input, $output['#markup']);
-    $this->assertEqual(array('file' => array($id => $id)), $output['#cache']['tags']);
+    $this->assertIdentical($input, $output->getProcessedText());
+    $this->assertEqual(array('file' => array($id)), $output->getCacheTags());
 
     $this->pass('One data-editor-file-uuid attribute with an invalid value.');
     $input = '<img src="llama.jpg" data-editor-file-uuid="invalid-' . $uuid . '" />';
     $output = $test($input);
-    $this->assertIdentical($input, $output['#markup']);
-    $this->assertEqual(array(), $output['#cache']['tags']);
+    $this->assertIdentical($input, $output->getProcessedText());
+    $this->assertEqual(array(), $output->getCacheTags());
 
     $this->pass('Two different data-editor-file-uuid attributes.');
     $input = '<img src="llama.jpg" data-editor-file-uuid="' . $uuid . '" />';
     $input .= '<img src="alpaca.jpg" data-editor-file-uuid="' . $uuid_2 . '" />';
     $output = $test($input);
-    $this->assertIdentical($input, $output['#markup']);
-    $this->assertEqual(array('file' => array($id => $id, $id_2 => $id_2)), $output['#cache']['tags']);
+    $this->assertIdentical($input, $output->getProcessedText());
+    $this->assertEqual(array('file' => array($id, $id_2)), $output->getCacheTags());
 
     $this->pass('Two identical  data-editor-file-uuid attributes.');
     $input = '<img src="llama.jpg" data-editor-file-uuid="' . $uuid . '" />';
     $input .= '<img src="llama.jpg" data-editor-file-uuid="' . $uuid . '" />';
     $output = $test($input);
-    $this->assertIdentical($input, $output['#markup']);
-    $this->assertEqual(array('file' => array($id => $id)), $output['#cache']['tags']);
+    $this->assertIdentical($input, $output->getProcessedText());
+    $this->assertEqual(array('file' => array($id)), $output->getCacheTags());
   }
 
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Common/RenderTest.php b/core/modules/system/lib/Drupal/system/Tests/Common/RenderTest.php
index caa80a2..0d23de1 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Common/RenderTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Common/RenderTest.php
@@ -825,7 +825,7 @@ function testDrupalRenderRenderCachePlaceholder() {
     $this->assertIdentical($token, $expected_token, 'The tokens are identical');
     // Verify the token is in the cached element.
     $expected_element = array(
-      '#markup' => '<foo><drupal:render-cache-placeholder callback="common_test_post_render_cache_placeholder" context="bar:' . $context['bar'] . ';token:' . $expected_token . ';" token="'. $expected_token . '" /></foo>',
+      '#markup' => '<foo><drupal-render-cache-placeholder callback="common_test_post_render_cache_placeholder" context="bar:' . $context['bar'] . ';token:' . $expected_token . ';" token="'. $expected_token . '"></drupal-render-cache-placeholder></foo>',
       '#post_render_cache' => array(
         'common_test_post_render_cache_placeholder' => array(
           $context
@@ -923,7 +923,7 @@ function testDrupalRenderChildElementRenderCachePlaceholder() {
     $this->assertIdentical($token, $expected_token, 'The tokens are identical for the child element');
     // Verify the token is in the cached element.
     $expected_element = array(
-      '#markup' => '<foo><drupal:render-cache-placeholder callback="common_test_post_render_cache_placeholder" context="bar:' . $context['bar'] . ';token:' . $expected_token . ';" token="'. $expected_token . '" /></foo>',
+      '#markup' => '<foo><drupal-render-cache-placeholder callback="common_test_post_render_cache_placeholder" context="bar:' . $context['bar'] . ';token:' . $expected_token . ';" token="'. $expected_token . '"></drupal-render-cache-placeholder></foo>',
       '#post_render_cache' => array(
         'common_test_post_render_cache_placeholder' => array(
           $context,
@@ -948,7 +948,7 @@ function testDrupalRenderChildElementRenderCachePlaceholder() {
     $this->assertIdentical($token, $expected_token, 'The tokens are identical for the parent element');
     // Verify the token is in the cached element.
     $expected_element = array(
-      '#markup' => '<div><foo><drupal:render-cache-placeholder callback="common_test_post_render_cache_placeholder" context="bar:' . $context['bar'] . ';token:' . $expected_token . ';" token="'. $expected_token . '" /></foo></div>' . "\n",
+      '#markup' => '<div><foo><drupal-render-cache-placeholder callback="common_test_post_render_cache_placeholder" context="bar:' . $context['bar'] . ';token:' . $expected_token . ';" token="'. $expected_token . '"></drupal-render-cache-placeholder></foo></div>' . "\n",
       '#post_render_cache' => array(
         'common_test_post_render_cache_placeholder' => array(
           $context,
@@ -977,7 +977,7 @@ function testDrupalRenderChildElementRenderCachePlaceholder() {
     $this->assertIdentical($token, $expected_token, 'The tokens are identical for the child element');
     // Verify the token is in the cached element.
     $expected_element = array(
-      '#markup' => '<foo><drupal:render-cache-placeholder callback="common_test_post_render_cache_placeholder" context="bar:' . $context['bar'] . ';token:' . $expected_token . ';" token="'. $expected_token . '" /></foo>',
+      '#markup' => '<foo><drupal-render-cache-placeholder callback="common_test_post_render_cache_placeholder" context="bar:' . $context['bar'] . ';token:' . $expected_token . ';" token="'. $expected_token . '"></drupal-render-cache-placeholder></foo>',
       '#post_render_cache' => array(
         'common_test_post_render_cache_placeholder' => array(
           $context,