Merged 9.0.6.

composer.lock

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

core/misc/ajax.es6.js

core/misc/ajax.js

core/misc/autocomplete.es6.js

core/misc/autocomplete.js

...ules/ckeditor/js/plugins/drupalimagecaption/plugin.es6.js

.../modules/ckeditor/js/plugins/drupalimagecaption/plugin.js

core/modules/file/src/Element/ManagedFile.php

core/modules/file/tests/src/Functional/FilePrivateTest.php

core/modules/filter/src/Plugin/Filter/FilterCaption.php

core/modules/user/src/Plugin/Block/UserLoginBlock.php

core/modules/workspaces/src/WorkspaceManager.php

...src/Functional/UpdateSystem/ActiveWorkspaceUpdateTest.php