diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index e1c15fe..6d9a30d 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -1621,8 +1621,8 @@ function format_string($string, array $args = array()) {
  * @see drupal_validate_utf8()
  * @ingroup sanitization
  */
-function check_plain($text) {
-  return htmlspecialchars($text, ENT_QUOTES, 'UTF-8');
+function check_plain($text, $double_encode = TRUE) {
+  return htmlspecialchars($text, ENT_QUOTES, 'UTF-8', $double_encode);
 }
 
 /**
diff --git a/core/lib/Drupal/Core/Template/AttributeString.php b/core/lib/Drupal/Core/Template/AttributeString.php
index 9776467..04b6c55 100644
--- a/core/lib/Drupal/Core/Template/AttributeString.php
+++ b/core/lib/Drupal/Core/Template/AttributeString.php
@@ -29,7 +29,8 @@ class AttributeString extends AttributeValueBase {
    */
   public function __toString() {
     $this->printed = TRUE;
-    return check_plain($this->value);
+    // Allow for the possibility of html entities in an attribute string
+    return check_plain($this->value, FALSE);
   }
 
 }
diff --git a/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php b/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php
index d4d7451..e331222 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Menu/MenuRouterTest.php
@@ -509,6 +509,7 @@ function testMenuLinkOptions() {
       'options' => array(
         'attributes' => array(
           'title' => 'Test title attribute',
+          'data_test' => '',
         ),
         'query' => array(
           'testparam' => 'testvalue',
@@ -520,6 +521,7 @@ function testMenuLinkOptions() {
     // Load front page.
     $this->drupalGet('test-page');
     $this->assertRaw('title="Test title attribute"', 'Title attribute of a menu link renders.');
+    $this->assertRaw('data_test=""', 'check_plain() does not double-escape entities in strings.');
     $this->assertRaw('testparam=testvalue', 'Query parameter added to menu link.');
   }