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.
The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.