The Ninja Forms - File Uploads Extension WordPress plugin is vulnerable to reflected cross-site scripting due to missing sanitization of the files filename parameter found in the ~/includes/ajax/controllers/uploads.php file which can be used by unauthenticated attackers to add malicious web scripts to vulnerable WordPress sites, in versions up to and including 3.3.12.
https://ninjaforms.com/extensions/file-uploads/?changelog=1/#:~:text=3.3.13%20(30%20November%202021)