Unrestricted Upload of File with Dangerous Type
The Ninja Forms - File Uploads Extension WordPress plugin is vulnerable to arbitrary file uploads due to insufficient input file type validation found in the ~/includes/ajax/controllers/uploads.php file which can be bypassed making it possible for unauthenticated attackers to upload malicious files that can be used to obtain remote code execution, in versions up to and including 3.3.0
CWE-434 - Unrestricted Upload of File with dangerous type
'Unrestricted file upload with dangerous type' attacks involve an attacker uploading or transferring files of dangerous types to the server. The severity of such an attack depends upon the execution mechanism and the storage location of the uploaded file. Thus, it may range from simple defacement to arbitrary file execution, and complete system takeover.