Ninja Forms Server-Side Validation Bypass via Client-Controlled Field Metadata Merge in AJAX Submission Handler

Ninja Forms WordPress plugin version 3.14.8 contains a client-side enforcement of server-side security vulnerability that allows unauthenticated attackers to bypass all form validation by merging attacker-controlled field metadata over server-loaded form definitions before validation runs. Attackers can craft a malicious AJAX submission overriding field types, removing required flags, and disabling CAPTCHA checks through the nopriv AJAX endpoint to trigger form actions such as email notifications and database storage with unverified, attacker-controlled content.