diff -u b/core/lib/Drupal/Core/Render/Element/MachineName.php b/core/lib/Drupal/Core/Render/Element/MachineName.php
--- b/core/lib/Drupal/Core/Render/Element/MachineName.php
+++ b/core/lib/Drupal/Core/Render/Element/MachineName.php
@@ -8,6 +8,7 @@
 namespace Drupal\Core\Render\Element;
 
 use Drupal\Component\Utility\NestedArray;
+use Drupal\Component\Utility\SafeMarkup;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Language\LanguageInterface;
 
@@ -151,13 +152,13 @@
     $element['#machine_name']['suffix'] = '#' . $suffix_id;
 
     if ($element['#machine_name']['standalone']) {
-      $element['#suffix'] = $element['#suffix'] . ' <small id="' . $suffix_id . '">&nbsp;</small>';
+      SafeMarkup::set($element['#suffix'] = $element['#suffix'] . ' <small id="' . $suffix_id . '">&nbsp;</small>');
     }
     else {
       // Append a field suffix to the source form element, which will contain
       // the live preview of the machine name.
       $source += array('#field_suffix' => '');
-      $source['#field_suffix'] = $source['#field_suffix'] . ' <small id="' . $suffix_id . '">&nbsp;</small>';
+      SafeMarkup::set($source['#field_suffix'] = $source['#field_suffix'] . ' <small id="' . $suffix_id . '">&nbsp;</small>');
 
       $parents = array_merge($element['#machine_name']['source'], array('#field_suffix'));
       NestedArray::setValue($form_state->getCompleteForm(), $parents, $source['#field_suffix']);
diff -u b/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
--- b/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -258,7 +258,7 @@
       '#type' => 'details',
       '#title' => SafeMarkup::set('<span class="text"> ' . drupal_render($module['description']) . '</span>'),
       '#attributes' => array('id' => $module['enable']['#id'] . '-description'),
-      '#description' => $description,
+      '#description' => SafeMarkup::set($description),
     );
     $col4 = drupal_render($details);
     $row[] = array('class' => array('description', 'expand'), 'data' => $col4);