Description

Additional CSS classes are not preserved in embed blocks.
At least, it was reproduced in the following blocks

• Twitter
• YouTube
• Flickr

In addition, Twitter will no longer preview correctly when additional CSS classes are entered.

Step-by-step reproduction instructions

N/A

Screenshots, screen recording, code snippet

N/A

Environment info

Gutenberg Version: 14.5.0-rc.1

Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes