# CVE-2026-100151: Ninja Forms Contact Form Builder DOM-based XSS in URL parameter

Source: https://junglewise.ai/threats/cve-2026-100151-the-ninja-forms-contact-form-builder-with-calculators-quizzes  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-31. Updated: 2026-10-31  
License: CC BY 4.0 with a link back

CVE-2026-100151 · Severity: medium · CVSS 6.1 · Published 2026-10-31

Ninja Forms is a WordPress plugin used to build and manage contact forms. An unauthenticated attacker can inject malicious scripts into web pages by crafting a malicious link with specially crafted URL parameters; if a user clicks the link, the injected script executes in their browser, potentially stealing data or session tokens.

Vendors: [Ninja Forms](https://junglewise.ai/threats/vendors/ninja-forms).

## Quick answers

**Is CVE-2026-100151 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-100151 being exploited in the wild.

**How severe is CVE-2026-100151?** Medium severity, with a CVSS score of 6.1, published 31 October 2026.

**Which products and versions are affected?** Ninja Forms – Contact Form Builder with Calculators, Quizzes, Signatures & AI Form Builder up to and including 3.15.5.

**Is there a fix for CVE-2026-100151?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-100151 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-100151?** Check whether you run Ninja Forms – Contact Form Builder with Calculators, Quizzes or Signatures & AI Form Builder at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The plugin is vulnerable to Reflected DOM-Based Cross-Site Scripting (XSS) via insufficient input sanitization and output escaping of 'querystring:<key>' URL parameters. When an attacker supplies a matching field:<key> URL parameter, the server-side sanitization is bypassed and the client-side JavaScript reconstructs field content directly from the raw query string, allowing arbitrary script injection. The vulnerability affects all versions up to and including 3.15.5.

## Affected products

- Ninja Forms Ninja Forms – Contact Form Builder with Calculators, Quizzes, Signatures & AI Form Builder up to and including 3.15.5

## Timeline

- 2026-10-31: disclosed

## References

- [https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/assets/js/min/front-end.js](https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/assets/js/min/front-end.js)
- [https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/includes/MergeTags/Other.php](https://plugins.trac.wordpress.org/browser/ninja-forms/tags/3.15.4/includes/MergeTags/Other.php)