Steps to reproduce the issue

Install Joomla 4.0.0 Beta1 with demo content
Login to the FRONTEND of the site as the new Super Admin
Navigate to the "About" article (or I guess any article) and click the edit button.
Click CMS Content in the wysiwyg
Click Image (model loads)
Click Create New Folder
Enter "test" as a folder name
Click create

Expected result

Folder with name "test" created.

Actual result

Model inside the model asking for the new folder name stays, the typed folder name is removed, the backdrop over the rest of the first model remains, but an red error message is shown under that saying "You are not authorised"

BONUS ISSUE: Make two or more errors and you see that the errors are pushed down with huge whitespace were it appears another error might/should/may be wanting to sit, but is not.

Same issue when attempting to upload images in the frontend.

Same issue deleting folders/images from frontend

System information (as much as possible)

Safari on Mac

Additional Information

The Ajax calls result with

{"success":false,"message":"The security token did not match. The request was aborted to prevent any security breach. Please try again.","messages":null,"data":null}