commit 27d196a1b0ee09c23e60c816a2a6aa5a25ff5198
Author: Joel Pittet <joel@pittet.ca>
Date:   Fri Apr 18 23:20:22 2014 -0700

    Found bits that were double escaping and marked them as raw/markup. Biggest change is that all _theme output is returned as safe markup because it's synonymous with including a template in a template.

diff --git a/core/includes/theme.inc b/core/includes/theme.inc
index da18b6a..7556a2f 100644
--- a/core/includes/theme.inc
+++ b/core/includes/theme.inc
@@ -632,7 +632,8 @@ function _theme($hook, $variables = array()) {
 
   // restore path_to_theme()
   $theme_path = $temp;
-  return (string) $output;
+
+  return new Markup($output);
 }
 
 /**
@@ -2079,7 +2080,7 @@ function template_preprocess_page(&$variables) {
 
   // Move some variables to the top level for themer convenience and template cleanliness.
   $variables['show_messages'] = $variables['page']['#show_messages'];
-  $variables['title'] = $variables['page']['#title'];
+  $variables['title'] = new Markup($variables['page']['#title']);
 
   foreach (system_region_list($GLOBALS['theme']) as $region_key => $region_name) {
     if (!isset($variables['page'][$region_key])) {
diff --git a/core/modules/color/templates/color-scheme-form.html.twig b/core/modules/color/templates/color-scheme-form.html.twig
index 6cfacbd..4d39743 100644
--- a/core/modules/color/templates/color-scheme-form.html.twig
+++ b/core/modules/color/templates/color-scheme-form.html.twig
@@ -22,5 +22,5 @@
   </div>
   {{ form }}
   <h2>{{ 'Preview'|t }}</h2>
-  {{ html_preview }}
+  {{ html_preview|raw }}
 </div>
diff --git a/core/modules/filter/templates/text-format-wrapper.html.twig b/core/modules/filter/templates/text-format-wrapper.html.twig
index f453971..c657117 100644
--- a/core/modules/filter/templates/text-format-wrapper.html.twig
+++ b/core/modules/filter/templates/text-format-wrapper.html.twig
@@ -11,7 +11,7 @@
  */
 #}
 <div class="text-format-wrapper form-item">
-  {{ children }}
+  {{ children|raw }}
   {% if description %}
     <div class="description">{{ description }}</div>
   {% endif %}
diff --git a/core/modules/system/templates/breadcrumb.html.twig b/core/modules/system/templates/breadcrumb.html.twig
index 5f322f9..d36a426 100644
--- a/core/modules/system/templates/breadcrumb.html.twig
+++ b/core/modules/system/templates/breadcrumb.html.twig
@@ -14,7 +14,7 @@
     <h2 class="visually-hidden">{{ 'You are here'|t }}</h2>
     <ol>
     {% for item in breadcrumb %}
-      <li>{{ item }}</li>
+      <li>{{ item|raw }}</li>
     {% endfor %}
     </ol>
   </nav>
diff --git a/core/modules/system/templates/checkboxes.html.twig b/core/modules/system/templates/checkboxes.html.twig
index 00384d3..d38a918 100644
--- a/core/modules/system/templates/checkboxes.html.twig
+++ b/core/modules/system/templates/checkboxes.html.twig
@@ -14,4 +14,4 @@
  @todo: remove this file once http://drupal.org/node/1819284 is resolved.
  This is identical to core/modules/system/templates/container.html.twig
 #}
-<div{{ attributes }}>{{ children }}</div>
+<div{{ attributes }}>{{ children|raw }}</div>
diff --git a/core/modules/system/templates/details.html.twig b/core/modules/system/templates/details.html.twig
index 17ea820..6283dc2 100644
--- a/core/modules/system/templates/details.html.twig
+++ b/core/modules/system/templates/details.html.twig
@@ -17,17 +17,17 @@
 #}
 <details{{ attributes }}>
   {%- if title -%}
-    <summary{{ summary_attributes }}>{{ title }}</summary>
+    <summary{{ summary_attributes }}>{{ title|raw }}</summary>
   {%- endif -%}
   <div class="details-wrapper">
     {%- if description -%}
-      <div class="details-description">{{ description }}</div>
+      <div class="details-description">{{ description|raw }}</div>
     {%- endif -%}
     {%- if children -%}
-      {{ children }}
+      {{ children|raw }}
     {%- endif -%}
     {%- if value -%}
-      {{ value }}
+      {{ value|raw }}
     {%- endif -%}
   </div>
 </details>
diff --git a/core/modules/system/templates/form-element.html.twig b/core/modules/system/templates/form-element.html.twig
index ea4d90f..788686a 100644
--- a/core/modules/system/templates/form-element.html.twig
+++ b/core/modules/system/templates/form-element.html.twig
@@ -52,7 +52,7 @@
   {% endif %}
   {% if description.content %}
     <div{{ description.attributes }}>
-      {{ description.content }}
+      {{ description.content|raw }}
     </div>
   {% endif %}
 </div>
diff --git a/core/modules/system/templates/radios.html.twig b/core/modules/system/templates/radios.html.twig
index e397644..01725b7 100644
--- a/core/modules/system/templates/radios.html.twig
+++ b/core/modules/system/templates/radios.html.twig
@@ -12,4 +12,4 @@
  * @ingroup themeable
  */
 #}
-<div{{ attributes }}>{{ children }}</div>
+<div{{ attributes }}>{{ children|raw }}</div>
diff --git a/core/modules/system/templates/select.html.twig b/core/modules/system/templates/select.html.twig
index 21f32ac..6a24ffd 100644
--- a/core/modules/system/templates/select.html.twig
+++ b/core/modules/system/templates/select.html.twig
@@ -12,4 +12,4 @@
  * @ingroup themeable
  */
 #}
-<select{{ attributes }}>{{ options }}</select>
+<select{{ attributes }}>{{ options|raw }}</select>
diff --git a/core/modules/system/templates/status-messages.html.twig b/core/modules/system/templates/status-messages.html.twig
index 505eb20..e86df24 100644
--- a/core/modules/system/templates/status-messages.html.twig
+++ b/core/modules/system/templates/status-messages.html.twig
@@ -34,11 +34,11 @@
       {% if messages|length > 1 %}
         <ul class="messages__list">
           {% for message in messages %}
-            <li class="messages__item">{{ message }}</li>
+            <li class="messages__item">{{ message|raw }}</li>
           {% endfor %}
         </ul>
       {% else %}
-        {{ messages.0 }}
+        {{ messages.0|raw }}
       {% endif %}
     {% if type == 'error' %}
       </div>
diff --git a/core/modules/views/templates/views-view-grid.html.twig b/core/modules/views/templates/views-view-grid.html.twig
index a5a813c..bfadb8e 100644
--- a/core/modules/views/templates/views-view-grid.html.twig
+++ b/core/modules/views/templates/views-view-grid.html.twig
@@ -31,7 +31,7 @@
   <div{{ row.attributes }}>
     {% for column in row.content %}
     <div{{ column.attributes }}>
-      {{ column.content }}
+      {{ column.content|raw }}
     </div>
     {% endfor %}
   </div>
@@ -41,7 +41,7 @@
   <div{{ column.attributes }}>
     {% for row in column.content %}
       <div{{ row.attributes }}>
-        {{ row.content }}
+        {{ row.content|raw }}
       </div>
     {% endfor %}
     </div>
diff --git a/core/modules/views/templates/views-view-table.html.twig b/core/modules/views/templates/views-view-table.html.twig
index 6b0b26c..7b1f280 100644
--- a/core/modules/views/templates/views-view-table.html.twig
+++ b/core/modules/views/templates/views-view-table.html.twig
@@ -51,7 +51,7 @@
       <tr>
         {% for column in header %}
           <th{{ column.attributes }} scope="col">
-            {{ column.content }}
+            {{ column.content|raw }}
           </th>
         {% endfor %}
       </tr>
@@ -62,7 +62,7 @@
       <tr{{ row.attributes }}>
         {% for column in row.columns %}
           <td{{ column.attributes }}>
-            {{ column.content }}
+            {{ column.content|raw }}
           </td>
         {% endfor %}
       </tr>