Just Custom Fields <= 3.3.2 - Missing Authorization via AJAX actions

The Just Custom Fields plugin for WordPress is vulnerable to unauthorized access of functionality due to a missing capability check on several AJAX functions in all versions up to, and including, 3.3.2. This makes it possible for authenticated attackers, with Subscriber-level access and above, to invoke this functionality intended for admin users. This enables subscribers to manage field groups, change visibility of items among other things.