CVE-2026-65051 in Ninja Forms Plugin
Summary
by MITRE • 07/21/2026
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.
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Analysis
by VulDB Data Team • 07/21/2026
This vulnerability resides in the Ninja Forms WordPress plugin version 3.14.8 where a critical client-side security enforcement flaw allows unauthenticated attackers to bypass all form validation mechanisms through a sophisticated metadata manipulation attack. The core technical issue stems from the plugin's failure to properly validate and sanitize field metadata that is transmitted from client-side to server-side components, creating a dangerous race condition where attacker-controlled data can override legitimate server-loaded configurations before any validation occurs.
The vulnerability operates through a specific exploitation vector involving the nopriv AJAX endpoint which is designed to handle unauthenticated form submissions. Attackers can craft malicious AJAX requests that merge their controlled field metadata over the server-loaded form definitions, effectively hijacking the form validation process. This manipulation allows adversaries to override critical field properties including field types, remove required validation flags, and disable CAPTCHA protection mechanisms that are essential for preventing automated abuse.
The operational impact of this vulnerability is severe as it enables attackers to trigger various form actions with completely unverified and attacker-controlled content. Specifically, malicious submissions can bypass email notification systems, database storage mechanisms, and other backend processes that typically require validated user input. This creates opportunities for spam injection, data corruption, and potential information disclosure through manipulated form submissions that appear legitimate to the server-side processing logic.
From a security standards perspective, this vulnerability aligns with CWE-601 URL Redirection to Untrusted Site ('Open Redirect') and CWE-352 Cross-Site Request Forgery (CSRF) categories as it involves unauthorized manipulation of server-side configurations through client-side data. The attack pattern also maps to ATT&CK technique T1213 Data from Information Repositories, where adversaries exploit application logic flaws to access or manipulate stored data through compromised form validation processes. Additionally, the vulnerability demonstrates characteristics of CWE-502 Deserialization of Untrusted Data when considering how attacker-controlled metadata can be merged with legitimate server configurations.
The mitigation strategy should focus on implementing robust server-side validation that prevents client-side metadata from overriding critical form configuration parameters during the validation phase. This requires enforcing strict input sanitization and validation procedures at multiple layers, ensuring that field definitions cannot be manipulated by unauthenticated users through AJAX requests. Additionally, the nopriv AJAX endpoint should implement proper authentication checks for operations that modify form behavior or trigger sensitive actions, and all form metadata merging processes must occur within secure server-side contexts that cannot be influenced by external client data.
Security practitioners should also consider implementing rate limiting and CAPTCHA enforcement mechanisms that operate independently of form configuration settings to prevent automated abuse of the vulnerable endpoint. Regular security audits of plugin code should specifically target validation logic and AJAX endpoint implementations to identify similar race condition vulnerabilities where client-side data can influence server-side processing workflows. The fix should ensure that all form validation processes execute with immutable server-loaded configurations that cannot be overridden through attacker-controlled metadata submissions, thereby maintaining the integrity of validation checks regardless of client-side input manipulation attempts.