diff --git a/core/modules/aggregator/src/Tests/AddFeedTest.php b/core/modules/aggregator/src/Tests/AddFeedTest.php
index 2a7f037..b66ac55 100644
--- a/core/modules/aggregator/src/Tests/AddFeedTest.php
+++ b/core/modules/aggregator/src/Tests/AddFeedTest.php
@@ -6,6 +6,7 @@
  */
 
 namespace Drupal\aggregator\Tests;
+use Drupal\Component\Utility\Html;
 
 /**
  * Add feed test.
@@ -45,6 +46,23 @@ public function testAddFeed() {
   }
 
   /**
+   * Ensures that the feed label is escaping when rendering the feed icon.
+   */
+  public function testFeedLabelEscaping() {
+    $feed = $this->createFeed(NULL, ['title[0][value]' => 'Test feed title <script>alert(123);</script>']);
+    $this->checkForMetaRefresh();
+
+    $this->drupalGet('aggregator/sources/' . $feed->id());
+    $this->assertResponse(200);
+
+    $result = $this->xpath('//h1');
+    $this->assertEqual((string) $result[0], 'Test feed title alert(123);');
+
+    // Ensure the feed icon title is escaped.
+    $this->assertRaw('class="feed-icon">  Subscribe to Test feed title &lt;script&gt;alert(123);&lt;/script&gt; feed</a>');
+  }
+
+  /**
    * Tests feeds with very long URLs.
    */
   public function testAddLongFeed() {
diff --git a/core/modules/simpletest/src/AssertContentTrait.php b/core/modules/simpletest/src/AssertContentTrait.php
index 87e8887..1457170 100644
--- a/core/modules/simpletest/src/AssertContentTrait.php
+++ b/core/modules/simpletest/src/AssertContentTrait.php
@@ -818,6 +818,23 @@ protected function assertTitle($title, $message = '', $group = 'Other') {
   }
 
   /**
+   * Assertion helper to check the raw content of a specific tag.
+   *
+   * This is needed because xpath html decodes stuff.
+   */
+  protected function assertRawTag($expected_html, $tag, array $classes = []) {
+    $attributes = '';
+    if ($classes) {
+      $attributes = '.*class="' . implode(' ', $classes) . '".*';
+    }
+    preg_match("@<$tag " . $attributes . ">([^<]*)</$tag>@", str_replace(["\n", "\r"], '', $this->getRawContent()), $matches);
+    debug("@<$tag " . $attributes . ">([^<]*)</$tag>@");
+    debug($matches);
+
+    debug($matches[1]);
+  }
+
+  /**
    * Pass if the page title is not the given string.
    *
    * @param string $title