Advanced Custom Fields 5.0-5.12.2 - Unauthenticated File Upload

The Advanced Custom Fields WordPress plugin before 5.12.3, Advanced Custom Fields Pro WordPress plugin before 5.12.3 allows unauthenticated users to upload files allowed in a default WP configuration (so PHP is not possible) if there is a frontend form available. This vulnerability was introduced in the 5.0 rewrite and did not exist prior to that release.