diff --git a/core/lib/Drupal/Core/Render/Renderer.php b/core/lib/Drupal/Core/Render/Renderer.php
index c2e03c9..41ac83f 100644
--- a/core/lib/Drupal/Core/Render/Renderer.php
+++ b/core/lib/Drupal/Core/Render/Renderer.php
@@ -435,7 +435,6 @@ protected function doRender(&$elements, $is_root_call = FALSE) {
     // Check the elements for insecure HTML and pass through sanitization.
     if (isset($elements)) {
       $markup_keys = array(
-        '#description',
         '#field_prefix',
         '#field_suffix',
       );
diff --git a/core/modules/entity_reference/src/Plugin/views/row/EntityReference.php b/core/modules/entity_reference/src/Plugin/views/row/EntityReference.php
index 3323933..b4fb085 100644
--- a/core/modules/entity_reference/src/Plugin/views/row/EntityReference.php
+++ b/core/modules/entity_reference/src/Plugin/views/row/EntityReference.php
@@ -43,6 +43,7 @@ public function buildOptionsForm(&$form, FormStateInterface $form_state) {
     parent::buildOptionsForm($form, $form_state);
 
     // Expand the description of the 'Inline field' checkboxes.
+    // @todo hmmm...
     $form['inline']['#description'] .= '<br />' . $this->t("<strong>Note:</strong> In 'Entity Reference' displays, all fields will be displayed inline unless an explicit selection of inline fields is made here." );
   }
 
diff --git a/core/modules/field_ui/src/Form/FieldConfigEditForm.php b/core/modules/field_ui/src/Form/FieldConfigEditForm.php
index ba972a9..7ea912c 100644
--- a/core/modules/field_ui/src/Form/FieldConfigEditForm.php
+++ b/core/modules/field_ui/src/Form/FieldConfigEditForm.php
@@ -65,7 +65,7 @@ public function form(array $form, FormStateInterface $form_state) {
       '#title' => $this->t('Help text'),
       '#default_value' => $this->entity->getDescription(),
       '#rows' => 5,
-      '#description' => $this->t('Instructions to present to the user below this field on the editing form.<br />Allowed HTML tags: @tags', array('@tags' => FieldFilteredString::displayAllowedTags())) . '<br />' . $this->t('This field supports tokens.'),
+      '#description' => $this->t('Instructions to present to the user below this field on the editing form.<br />Allowed HTML tags: @tags<br />This field supports tokens.', array('@tags' => FieldFilteredString::displayAllowedTags())),
       '#weight' => -10,
     );
 
diff --git a/core/modules/options/src/Plugin/Field/FieldType/ListItemBase.php b/core/modules/options/src/Plugin/Field/FieldType/ListItemBase.php
index bbca170..fddae99 100644
--- a/core/modules/options/src/Plugin/Field/FieldType/ListItemBase.php
+++ b/core/modules/options/src/Plugin/Field/FieldType/ListItemBase.php
@@ -101,7 +101,7 @@ public function storageSettingsForm(array &$form, FormStateInterface $form_state
       '#allowed_values' => $allowed_values,
     );
 
-    $element['allowed_values']['#description'] = $this->allowedValuesDescription();
+    $element['allowed_values']['#description'] = ['#markup' => $this->allowedValuesDescription()];
 
     $element['allowed_values_function'] = array(
       '#type' => 'item',
diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index 11b72a5..9ff8fe9 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -261,7 +261,9 @@ function theme_system_modules_details($variables) {
       '#type' => 'details',
       '#title' => $title,
       '#attributes' => array('id' => $module['enable']['#id'] . '-description'),
-      '#description' => $description,
+      // #description is built up using lots of markup therefore we need to
+      // XSS admin filter it instead of auto-escape.
+      '#description' => ['#markup' => $description],
     );
     $row[] = ['class' => ['description', 'expand'], 'data' => $details];
 
diff --git a/core/modules/views/src/Plugin/EntityReferenceSelection/ViewsSelection.php b/core/modules/views/src/Plugin/EntityReferenceSelection/ViewsSelection.php
index 25e7393..d643bf7 100644
--- a/core/modules/views/src/Plugin/EntityReferenceSelection/ViewsSelection.php
+++ b/core/modules/views/src/Plugin/EntityReferenceSelection/ViewsSelection.php
@@ -67,7 +67,12 @@ public function buildConfigurationForm(array $form, FormStateInterface $form_sta
         '#required' => TRUE,
         '#options' => $options,
         '#default_value' => $default,
-        '#description' => '<p>' . $this->t('Choose the view and display that select the entities that can be referenced.<br />Only views with a display of type "Entity Reference" are eligible.') . '</p>',
+        '#description' => [
+          // @todo should we really be wrapping in <p>?
+          '#prefix' => '<p>',
+          '#markup' => $this->t('Choose the view and display that select the entities that can be referenced.<br />Only views with a display of type "Entity Reference" are eligible.'),
+          '#suffix' => '</p>',
+        ],
       );
 
       $default = !empty($view_settings['arguments']) ? implode(', ', $view_settings['arguments']) : '';
diff --git a/core/modules/views/src/Plugin/views/argument_default/ArgumentDefaultPluginBase.php b/core/modules/views/src/Plugin/views/argument_default/ArgumentDefaultPluginBase.php
index b5c2adf..72a7a67 100644
--- a/core/modules/views/src/Plugin/views/argument_default/ArgumentDefaultPluginBase.php
+++ b/core/modules/views/src/Plugin/views/argument_default/ArgumentDefaultPluginBase.php
@@ -98,6 +98,7 @@ protected function checkAccess(&$form, $option_name) {
     if (!$this->access()) {
       $form[$option_name]['#disabled'] = TRUE;
       $form[$option_name]['#value'] = $form[$this->option_name]['#default_value'];
+      // @todo - hmmm what.
       $form[$option_name]['#description'] .= ' <strong>' . $this->t('Note: you do not have permission to modify this. If you change the default filter type, this setting will be lost and you will NOT be able to get it back.') . '</strong>';
     }
   }
diff --git a/core/modules/views/src/Plugin/views/argument_validator/ArgumentValidatorPluginBase.php b/core/modules/views/src/Plugin/views/argument_validator/ArgumentValidatorPluginBase.php
index 7a6cf67..f83da27 100644
--- a/core/modules/views/src/Plugin/views/argument_validator/ArgumentValidatorPluginBase.php
+++ b/core/modules/views/src/Plugin/views/argument_validator/ArgumentValidatorPluginBase.php
@@ -93,6 +93,7 @@ protected function checkAccess(&$form, $option_name) {
     if (!$this->access()) {
       $form[$option_name]['#disabled'] = TRUE;
       $form[$option_name]['#value'] = $form[$this->option_name]['#default_value'];
+      // @todo - hmmm what.
       $form[$option_name]['#description'] .= ' <strong>' . $this->t('Note: you do not have permission to modify this. If you change the default filter type, this setting will be lost and you will NOT be able to get it back.') . '</strong>';
     }
   }