Maxi Blocks <= 2.1.8 - Missing Authorization to Authenticated (Author+) Media File Deletion via 'old_media_src' Parameter

The MaxiBlocks Builder plugin for WordPress is vulnerable to arbitrary media file deletion due to insufficient file ownership validation on the 'maxi_remove_custom_image_size' AJAX action in all versions up to, and including, 2.1.8. This makes it possible for authenticated attackers, with Author-level access and above, to delete arbitrary files in the wp-content/uploads directory, including files uploaded by other users and administrators.