Issue #3320467 by Liam Morland, nicrodgers, smustgrave, andypost, jonnyhocks, alexpott: form_build_id is a hidden input field and therefore should not have the autocomplete attribute

core/lib/Drupal/Core/Form/FormBuilder.php

@@ -729,17 +729,6 @@ class FormBuilder implements FormBuilderInterface, FormValidatorInterface, FormS
       // submitted form value appears literally, regardless of custom #tree
       // and #parents being set elsewhere.
       '#parents' => ['form_build_id'],
-      // Prevent user agents from prefilling the build ID with earlier values.
-      // When the ajax command "update_build_id" is executed, the user agent
-      // will assume that a user interaction changed the field. Upon a soft
-      // reload of the page, the previous build ID will be restored in the
-      // input, causing subsequent ajax callbacks to access the wrong cached
-      // form build. Setting the autocomplete attribute to "off" will tell the
-      // user agent to never reuse the value.
-      // @see https://www.w3.org/TR/2011/WD-html5-20110525/common-input-element-attributes.html#the-autocomplete-attribute
-      '#attributes' => [
-        'autocomplete' => 'off',
-      ],
     ];
 
     // Add a token, based on either #token or form_id, to any form displayed to