The Chatterbug Forms – Fast, Flexible WordPress Form Builder plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 1.0.2 via the cbforms_check_form_submissions function. This is due to missing server-side file extension validation in cbforms_check_form_submissions(), where the allowed-type check defaults to the uploaded file's own extension when no field restriction is configured, trivially allowing any extension including .php. This makes it possible for unauthenticated attackers to upload files that may be executable, which makes remote code execution possible. The submission nonce printed inline on every public page containing a Chatterbug form is freely obtainable by unauthenticated visitors and therefore does not constitute an effective access control barrier.