SimpleForm <= 3.10.2 - Unauthenticated Arbitrary File Upload via Trailing-Dot Filename via Unknown File Key in simpleform_get_submit_data

The SimpleForm – Form Maker to Chat Apps with Quiz, Poll and Multi Lead Notifications plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 3.10.2 via the handle_upload function. This is due to missing server-side file key allowlist and pre-sanitization extension derivation that allows a trailing-dot filename to bypass all extension and MIME validation in handle_upload. This makes it possible for unauthenticated attackers to upload files that may be executable, which makes remote code execution possible. The only access control is a nonce that is printed into every public form's data-nonce attribute, making it trivially obtainable by any unauthenticated visitor on a page embedding the form shortcode.