.../CKEditor5AllowedTagsTest.php                   | 11 +++----
 .../src/FunctionalJavascript/CKEditor5Test.php     | 36 ++++++++++++++++++++++
 2 files changed, 41 insertions(+), 6 deletions(-)

diff --git a/core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5AllowedTagsTest.php b/core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5AllowedTagsTest.php
index f67242f4e6..80b0636fcf 100644
--- a/core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5AllowedTagsTest.php
+++ b/core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5AllowedTagsTest.php
@@ -435,7 +435,7 @@ public function testFullHtml() {
     // Add a node with text rendered via the Plain Text format.
     $this->drupalGet('node/add');
     $page->fillField('title[0][value]', 'My test content');
-    $page->fillField('body[0][value]', '<p dir="ltr"><a style="color:#ff0000;" foo="bar" hreflang="en" href="https://example.com"><abbr title="National Aeronautics and Space Administration">NASA</abbr> is an acronym.</a></p>');
+    $page->fillField('body[0][value]', '<p><a style="color:#ff0000;" foo="bar" hreflang="en" href="https://example.com"><abbr title="National Aeronautics and Space Administration">NASA</abbr> is an acronym.</a></p>');
     $page->pressButton('Save');
 
     // Configure Full HTML text format to use CKEditor 5.
@@ -458,8 +458,7 @@ public function testFullHtml() {
 
     // But note that the `style` attribute was stripped by
     // \Drupal\editor\EditorXssFilter\Standard.
-    var_dump($this->getRawContent());
-    $assert_session->responseContains('<p dir="ltr"><a href="https://example.com" hreflang="en" foo="bar"><abbr title="National Aeronautics and Space Administration">NASA</abbr> is an acronym.</a></p>');
+    $assert_session->responseContains('<p><a href="https://example.com" hreflang="en" foo="bar"><abbr title="National Aeronautics and Space Administration">NASA</abbr> is an acronym.</a></p>');
 
     // Ensure attributes are retained after enabling link plugin.
     $this->drupalGet('admin/config/content/formats/manage/full_html');
@@ -471,7 +470,7 @@ public function testFullHtml() {
     $this->drupalGet('node/1/edit');
     $page->pressButton('Save');
 
-    $assert_session->responseContains('<p dir="ltr"><a href="https://example.com" hreflang="en" foo="bar"><abbr title="National Aeronautics and Space Administration">NASA</abbr> is an acronym.</a></p>');
+    $assert_session->responseContains('<p><a href="https://example.com" hreflang="en" foo="bar"><abbr title="National Aeronautics and Space Administration">NASA</abbr> is an acronym.</a></p>');
 
     // Configure Basic HTML text format to use CKE5 and enable the link plugin.
     $this->drupalGet('admin/config/content/formats/manage/basic_html');
@@ -493,8 +492,8 @@ public function testFullHtml() {
     $page->pressButton('Save');
 
     // The `style` and foo` attributes should have been removed, as should the
-    // `<abbr>` tag. But the `dir="ltr"` attribute should have been retained.
-    $assert_session->responseContains('<p dir="ltr"><a href="https://example.com" hreflang="en">NASA is an acronym.</a></p>');
+    // `<abbr>` tag.
+    $assert_session->responseContains('<p><a href="https://example.com" hreflang="en">NASA is an acronym.</a></p>');
   }
 
 }
diff --git a/core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5Test.php b/core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5Test.php
index 7a8dcb56c4..c01c81a360 100644
--- a/core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5Test.php
+++ b/core/modules/ckeditor5/tests/src/FunctionalJavascript/CKEditor5Test.php
@@ -8,6 +8,7 @@
 use Drupal\file\Entity\File;
 use Drupal\filter\Entity\FilterFormat;
 use Drupal\node\Entity\Node;
+use Drupal\Tests\ckeditor5\Traits\CKEditor5TestTrait;
 use Drupal\Tests\TestFileCreationTrait;
 use Drupal\user\RoleInterface;
 use Symfony\Component\Validator\ConstraintViolation;
@@ -22,6 +23,7 @@
  */
 class CKEditor5Test extends CKEditor5TestBase {
 
+  use CKEditor5TestTrait;
   use TestFileCreationTrait;
 
   /**
@@ -432,4 +434,38 @@ public function testEmphasis() {
     $assert_session->responseContains('<p>This is a <em>test!</em></p>');
   }
 
+  /**
+   * Ensures that CKEditor 5 retains filter_html's allowed global attributes.
+   *
+   * FilterHtml always forbids the `style` and `on*` attributes, and always
+   * allows the `lang` attribute (with any value) and the `dir` attribute (with
+   * either `ltr` or `rtl` as value). It's important that those last two
+   * attributes are guaranteed to be retained.
+   *
+   * @see \Drupal\filter\Plugin\Filter\FilterHtml::getHTMLRestrictions()
+   */
+  public function testFilterHtmlAllowedGlobalAttributes(): void {
+    $page = $this->getSession()->getPage();
+    $assert_session = $this->assertSession();
+
+    // Add a node with text rendered via the Plain Text format.
+    $this->drupalGet('node/add');
+    $page->fillField('title[0][value]', 'Multilingual Hello World');
+    $page->fillField('body[0][value]', '<p dir="ltr">Hello World></p><p dir="rtl">مرحبا بالعالم</p>');
+    $page->pressButton('Save');
+
+    $this->createNewTextFormat($page, $assert_session);
+    $this->saveNewTextFormat($page, $assert_session);
+
+    $this->drupalGet('node/1/edit');
+    $page->selectFieldOption('body[0][format]', 'ckeditor5');
+    $this->assertNotEmpty($assert_session->waitForText('Change text format?'));
+    $page->pressButton('Continue');
+
+    $this->waitForEditor();
+    $page->pressButton('Save');
+
+    $assert_session->responseContains('<p dir="ltr">Hello World></p><p dir="rtl">مرحبا بالعالم</p>');
+  }
+
 }