diff -u b/core/tests/Drupal/Tests/Core/Render/Element/HtmlTagTest.php b/core/tests/Drupal/Tests/Core/Render/Element/HtmlTagTest.php
--- b/core/tests/Drupal/Tests/Core/Render/Element/HtmlTagTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/Element/HtmlTagTest.php
@@ -99,6 +99,15 @@
     );
     $tags[] = array($element, "<p>value</p>\n");
 
+    // Ensure that #value_prefix and #value_suffix are not filtered.
+    $element = array(
+      '#tag' => 'p',
+      '#value' => 'value',
+      '#value_prefix' => '<script>value</script>',
+      '#value_suffix' => '<script>value</script>',
+    );
+    $tags[] = array($element, "<p><script>value</script>value<script>value</script></p>\n");
+
     return $tags;
   }