diff --git a/core/includes/common.inc b/core/includes/common.inc
index 1581de6..88f16fd 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -20,6 +20,7 @@
 use Drupal\Component\Utility\String;
 use Drupal\Component\Utility\Tags;
 use Drupal\Component\Utility\UrlHelper;
+use Drupal\Component\Utility\Xss;
 use Drupal\Core\Cache\Cache;
 use Drupal\Core\Language\LanguageInterface;
 use Drupal\Core\Render\RenderStackFrame;
@@ -2765,6 +2766,22 @@ function drupal_render(&$elements, $is_recursive_call = FALSE) {
     $elements += element_info($elements['#type']);
   }
 
+  // Filtering keys which are expected to contain HTML.
+  $markup_keys = array(
+    '#description',
+    '#field_prefix',
+    '#field_suffix',
+    '#prefix',
+    '#suffix',
+  );
+  foreach ($markup_keys as $key) {
+    // If it's not scalar it can deal with itself through __toString()
+    // or drupal_render().
+    if (!empty($elements[$key]) && is_scalar($elements[$key]) && !SafeMarkup::isSafe($elements[$key])) {
+      $elements[$key] = Xss::filterAdmin($elements[$key]);
+    }
+  }
+
   // Make any final changes to the element before it is rendered. This means
   // that the $element or the children can be altered or corrected before the
   // element is rendered into the final text.
@@ -2896,6 +2913,7 @@ function drupal_render(&$elements, $is_recursive_call = FALSE) {
   // #cache is disabled, #cache is enabled, there is a cache hit or miss.
   $prefix = isset($elements['#prefix']) ? $elements['#prefix'] : '';
   $suffix = isset($elements['#suffix']) ? $elements['#suffix'] : '';
+
   $elements['#markup'] = $prefix . $elements['#children'] . $suffix;
 
   // We've rendered this element (and its subtree!), now update the stack.
diff --git a/core/modules/field_ui/src/Tests/FieldUiTestBase.php b/core/modules/field_ui/src/Tests/FieldUiTestBase.php
index 962acec..314cf5b 100644
--- a/core/modules/field_ui/src/Tests/FieldUiTestBase.php
+++ b/core/modules/field_ui/src/Tests/FieldUiTestBase.php
@@ -105,6 +105,7 @@ function fieldUIAddExistingField($bundle_path, $initial_edit, $field_edit = arra
 
     // First step : 'Re-use existing field' on the 'Manage fields' page.
     $this->drupalPostForm("$bundle_path/fields", $initial_edit, t('Save'));
+    $this->assertNoRaw('<', 'The page does not have double escaped HTML tags.');
 
     // Second step : 'Field settings' form.
     $this->drupalPostForm(NULL, $field_edit, t('Save settings'));
diff --git a/core/modules/locale/src/Form/ImportForm.php b/core/modules/locale/src/Form/ImportForm.php
index eda1567..d9a811c 100644
--- a/core/modules/locale/src/Form/ImportForm.php
+++ b/core/modules/locale/src/Form/ImportForm.php
@@ -103,18 +103,22 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       'file_validate_extensions' => array('po'),
       'file_validate_size' => array(file_upload_max_size()),
     );
+
+    $file_description = array(
+      '#theme' => 'file_upload_help',
+      '#description' => $this->t('A Gettext Portable Object file.'),
+      '#upload_validators' => $validators,
+    );
+
     $form['file'] = array(
       '#type' => 'file',
       '#title' => $this->t('Translation file'),
-      '#description' => array(
-        '#theme' => 'file_upload_help',
-        '#description' => $this->t('A Gettext Portable Object file.'),
-        '#upload_validators' => $validators,
-      ),
+      '#description' => drupal_render($file_description),
       '#size' => 50,
       '#upload_validators' => $validators,
       '#attributes' => array('class' => array('file-import-input')),
     );
+
     $form['langcode'] = array(
       '#type' => 'select',
       '#title' => $this->t('Language'),
diff --git a/core/modules/options/src/Tests/OptionsFieldUITest.php b/core/modules/options/src/Tests/OptionsFieldUITest.php
index e3b4684..40343bf 100644
--- a/core/modules/options/src/Tests/OptionsFieldUITest.php
+++ b/core/modules/options/src/Tests/OptionsFieldUITest.php
@@ -278,6 +278,7 @@ protected function createOptionsField($type) {
   function assertAllowedValuesInput($input_string, $result, $message) {
     $edit = array('field_storage[settings][allowed_values]' => $input_string);
     $this->drupalPostForm($this->admin_path, $edit, t('Save field settings'));
+    $this->assertNoRaw('<', 'The page does not have double escaped HTML tags.');
 
     if (is_string($result)) {
       $this->assertText($result, $message);
diff --git a/core/modules/rdf/rdf.module b/core/modules/rdf/rdf.module
index f407e83..5ffd203 100644
--- a/core/modules/rdf/rdf.module
+++ b/core/modules/rdf/rdf.module
@@ -506,7 +506,7 @@ function rdf_preprocess_comment(&$variables) {
       '#theme' => 'rdf_metadata',
       '#metadata' => $variables['rdf_metadata_attributes'],
     );
-    $variables['content']['comment_body']['#prefix'] = drupal_render($rdf_metadata) . $variables['content']['comment_body']['#prefix'];
+    $variables['content']['comment_body']['#prefix'] = SafeMarkup::set(drupal_render($rdf_metadata) . $variables['content']['comment_body']['#prefix']);
   }
 }
 
diff --git a/core/modules/system/src/Tests/Common/RenderTest.php b/core/modules/system/src/Tests/Common/RenderTest.php
index d07085c..474be4c 100644
--- a/core/modules/system/src/Tests/Common/RenderTest.php
+++ b/core/modules/system/src/Tests/Common/RenderTest.php
@@ -9,6 +9,7 @@
 
 use Drupal\Component\Serialization\Json;
 use Drupal\Component\Utility\Html;
+use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Render\Element;
 use Drupal\simpletest\DrupalUnitTestBase;
 
@@ -782,14 +783,15 @@ function testDrupalRenderRenderCachePlaceholder() {
         ),
       ),
       '#markup' => $placeholder,
-      '#prefix' => '<foo>',
-      '#suffix' => '</foo>'
+      '#prefix' => SafeMarkup::set('<foo>'),
+      '#suffix' => SafeMarkup::set('</foo>'),
     );
     $expected_output = '<foo><bar>' . $context['bar'] . '</bar></foo>';
 
     // #cache disabled.
     $element = $test_element;
     $output = drupal_render($element);
+    $this->verbose($output);
     $this->assertIdentical($output, $expected_output, 'Placeholder was replaced in output');
     $expected_js = [
       ['type' => 'setting', 'data' => ['common_test' => $context]],