The GB Forms DB plugin for WordPress is vulnerable to Remote Code Execution in all versions up to, and including, 1.0.2 via the gbfdb_talk_to_front() function. This is due to the function accepting user input and then passing that through call_user_func(). This makes it possible for unauthenticated attackers to execute code on the server which can be leverage to inject backdoors or create new administrative user accounts to name a few things.
https://plugins.trac.wordpress.org/browser/gb-forms-db/trunk/core/functions.php#L367
https://plugins.trac.wordpress.org/browser/gb-forms-db/trunk/core/functions.php#L334