diff --git a/core/lib/Drupal/Core/Menu/MenuLinkManager.php b/core/lib/Drupal/Core/Menu/MenuLinkManager.php
index 44eeeb3..0cc7727 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkManager.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkManager.php
@@ -44,7 +44,8 @@ class MenuLinkManager implements MenuLinkManagerInterface {
     // The static title for the menu link. If this came from a YAML definition
     // or other safe source this may be a TranslationWrapper object.
     'title' => '',
-    // The description.
+    // The description. If this came from a YAML definition or other safe source
+    // this maybe be a TranslationWrapper object.
     'description' => '',
     // The plugin ID of the parent link (or NULL for a top-level link).
     'parent' => '',
diff --git a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
index 11e3711..92b5454 100644
--- a/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
+++ b/core/lib/Drupal/Core/Menu/MenuTreeStorage.php
@@ -1250,14 +1250,14 @@ protected static function schemaDefinition() {
           'default' => '',
         ),
         'title' => array(
-          'description' => 'The title for the link. May be a serialized TranslationWrapper',
+          'description' => 'The serialized title for the link. May be a TranslationWrapper',
           'type' => 'blob',
           'size' => 'big',
           'not null' => FALSE,
           'serialize' => TRUE,
         ),
         'description' => array(
-          'description' => 'The description of this link - used for admin pages and title attribute.',
+          'description' => 'The serialized description of this link - used for admin pages and title attribute. May be a TranslationWrapper.',
           'type' => 'blob',
           'size' => 'big',
           'not null' => FALSE,
diff --git a/core/modules/system/src/Tests/Menu/MenuLinkSecurityTest.php b/core/modules/system/src/Tests/Menu/MenuLinkSecurityTest.php
new file mode 100644
index 0000000..2fe6c3b
--- /dev/null
+++ b/core/modules/system/src/Tests/Menu/MenuLinkSecurityTest.php
@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Menu\MenuLinkSecurityTest.
+ */
+
+namespace Drupal\system\Tests\Menu;
+
+use Drupal\menu_link_content\Entity\MenuLinkContent;
+use Drupal\simpletest\WebTestBase;
+
+/**
+ * Ensures that menu links don't cause XSS issues.
+ *
+ * @group Menu
+ */
+class MenuLinkSecurityTest extends WebTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['menu_link_content', 'block', 'menu_test'];
+
+  /**
+   * ensures that a menu link does not cause an XSS issue.
+   */
+  public function testMenuLink() {
+    $menu_link_content = MenuLinkContent::create([
+      'title' => '<script>alert("Wild animals")</script>',
+      'menu_name' => 'tools',
+      'link' => ['uri' => 'route:<front>'],
+    ]);
+    $menu_link_content->save();
+
+    $this->drupalPlaceBlock('system_menu_block:tools');
+
+    $this->drupalGet('<front>');
+    $this->assertNoRaw('<script>alert("Wild animals")</script>');
+    $this->assertNoRaw('<script>alert("Even more wild animals")</script>');
+    $this->assertRaw(htmlspecialchars('<script>alert("Wild animals")</script>', ENT_QUOTES, 'UTF-8'));
+    $this->assertRaw(htmlspecialchars('<script>alert("Even more wild animals")</script>', ENT_QUOTES, 'UTF-8'));
+  }
+
+}
diff --git a/core/modules/system/src/Tests/Update/MenuTreeSerializationTitleTest.php b/core/modules/system/src/Tests/Update/MenuTreeSerializationTitleTest.php
new file mode 100644
index 0000000..b9e247f
--- /dev/null
+++ b/core/modules/system/src/Tests/Update/MenuTreeSerializationTitleTest.php
@@ -0,0 +1,49 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\system\Tests\Update\MenuTreeSerializationTitleTest.
+ */
+
+namespace Drupal\system\Tests\Update;
+
+/**
+ * Tests system_update_8001().
+ *
+ * @group Update
+ */
+class MenuTreeSerializationTitleTest extends UpdatePathTestBase {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function setUp() {
+    $this->databaseDumpFiles = [
+      __DIR__ . '/../../../tests/fixtures/update/drupal-8.bare.standard.php.gz',
+    ];
+    parent::setUp();
+  }
+
+  /**
+   * Ensures that the system_update_8001() runs as expected.
+   */
+  public function testUpdate() {
+    $this->runUpdates();
+
+    // Ensure that some fields got dropped.
+    $this->assertFalse(db_field_exists('menu_tree', 'title_arguments'));
+    $this->assertFalse(db_field_exists('menu_tree', 'title_contexts'));
+
+    // Ensure that all titles/descriptions are unserializable.
+    $select = \Drupal::database()->select('menu_tree');
+    $result = $select->fields('menu_tree', ['mlid', 'title', 'description'])
+      ->execute()
+      ->fetchAllAssoc('mlid');
+
+    foreach ($result as $link) {
+      unserialize($link->title);
+      unserialize($link->description);
+    }
+  }
+
+}
diff --git a/core/modules/system/src/Tests/Update/UpdatePathTestBase.php b/core/modules/system/src/Tests/Update/UpdatePathTestBase.php
index d152432..a9e0ad2 100644
--- a/core/modules/system/src/Tests/Update/UpdatePathTestBase.php
+++ b/core/modules/system/src/Tests/Update/UpdatePathTestBase.php
@@ -141,15 +141,7 @@ protected function setUp() {
 
     // Rebuild and reset.
     $this->rebuildAll();
-    // Remove the notices we get due to the menu link rebuild prior to running
-    // the system updates for the schema change.
-    foreach ($this->assertions as $key => $assertion) {
-      if ($assertion['message_group'] == 'Notice' && basename($assertion['file']) == 'MenuTreeStorage.php' && strpos($assertion['message'], 'unserialize(): Error at offset 0') !== FALSE) {
-        unset($this->assertions[$key]);
-        $this->deleteAssert($assertion['message_id']);
-        $this->results['#exception']--;
-      }
-    }
+
     // Replace User 1 with the user created here.
     /** @var \Drupal\user\UserInterface $account */
     $account = User::load(1);
@@ -207,4 +199,21 @@ protected function runUpdates() {
     $this->clickLink(t('Apply pending updates'));
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  protected function rebuildAll() {
+    parent::rebuildAll();
+
+    // Remove the notices we get due to the menu link rebuild prior to running
+    // the system updates for the schema change.
+    foreach ($this->assertions as $key => $assertion) {
+      if ($assertion['message_group'] == 'Notice' && basename($assertion['file']) == 'MenuTreeStorage.php' && strpos($assertion['message'], 'unserialize(): Error at offset 0') !== FALSE) {
+        unset($this->assertions[$key]);
+        $this->deleteAssert($assertion['message_id']);
+        $this->results['#exception']--;
+      }
+    }
+  }
+
 }
diff --git a/core/modules/system/system.install b/core/modules/system/system.install
index c3990c8..2f51cc0 100644
--- a/core/modules/system/system.install
+++ b/core/modules/system/system.install
@@ -1130,7 +1130,7 @@ function system_update_8001(&$sandbox = NULL) {
         ->condition('mlid', $menu_link['mlid'])
         ->execute();
 
-      $sandbox['current'] += 50;
+      $sandbox['current']++;;
     }
 
     $sandbox['#finished'] = empty($sandbox['max']) ? 1 : ($sandbox['current'] / $sandbox['max']);
@@ -1144,7 +1144,7 @@ function system_update_8001(&$sandbox = NULL) {
     return t('Menu links converted');
   }
   else {
-    return t('Menu link conversion skipped');
+    return t('Menu link conversion skipped, because the {menu_tree} table did not existed yet.');
   }
 }
 
diff --git a/core/modules/system/tests/modules/menu_test/menu_test.links.menu.yml b/core/modules/system/tests/modules/menu_test/menu_test.links.menu.yml
index 914fbd5..613bc92 100644
--- a/core/modules/system/tests/modules/menu_test/menu_test.links.menu.yml
+++ b/core/modules/system/tests/modules/menu_test/menu_test.links.menu.yml
@@ -79,3 +79,7 @@ menu_test.child:
   title: 'Test menu_name child'
   route_name: menu_test.menu_name_test
   parent: menu_test.parent
+
+menu_test.unsafe:
+  route_name: menu_test.menu_name_test
+  deriver: '\Drupal\menu_test\Plugin\Derivative\MenuLinkTestWithUnsafeTitle'
diff --git a/core/modules/system/tests/modules/menu_test/src/Plugin/Derivative/MenuLinkTestWithUnsafeTitle.php b/core/modules/system/tests/modules/menu_test/src/Plugin/Derivative/MenuLinkTestWithUnsafeTitle.php
new file mode 100644
index 0000000..a9d9041
--- /dev/null
+++ b/core/modules/system/tests/modules/menu_test/src/Plugin/Derivative/MenuLinkTestWithUnsafeTitle.php
@@ -0,0 +1,30 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\menu_test\Plugin\Derivative\MenuLinkTestWithUnsafeTitle.
+ */
+
+namespace Drupal\menu_test\Plugin\Derivative;
+
+use Drupal\Component\Plugin\Derivative\DeriverBase;
+
+/**
+ * Test derivative with an unsafe string.
+ */
+class MenuLinkTestWithUnsafeTitle extends DeriverBase {
+
+  /**
+   * @inheritDoc
+   */
+  public function getDerivativeDefinitions($base_plugin_definition) {
+    $this->derivatives['unsafe'] = [
+        'title' => '<script>alert("Even more wild animals")</script>',
+        'menu_name' => 'tools',
+      ] + $base_plugin_definition;
+
+    return $this->derivatives;
+  }
+
+
+}