The Revision Manager TMC plugin for WordPress is vulnerable to unauthorized arbitrary email sending due to a missing capability check on the _a_ajaxQuickEmailTestCallback() function in all versions up to, and including, 2.8.19. This makes it possible for authenticated attackers, with subscriber-level access and above, to send emails with arbitrary content to any individual through the vulnerable web server.
The product does not perform an authorization check when an actor attempts to access a resource or perform an action.