# CVE-2026-89435: Formidable Forms arbitrary plugin installation vulnerability

Source: https://junglewise.ai/threats/cve-2026-89435-the-formidable-forms-wordpress-form-builder-for-contact-forms  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-30. Updated: 2026-10-30  
License: CC BY 4.0 with a link back

CVE-2026-89435 · Severity: high · CVSS 8.8 · Published 2026-10-30

Formidable Forms is a WordPress form-building plugin used to create contact forms, quizzes, and calculators. The plugin contains a flaw that allows attackers with basic subscriber-level access to install malicious plugins on a WordPress site, giving them complete control over the website and its data. The vulnerability only affects free installations without the Pro version.

Technologies: [Formidable Forms](https://junglewise.ai/threats/technologies/formidable-forms). Vendors: [Formidable](https://junglewise.ai/threats/vendors/formidable).

## Quick answers

**Is CVE-2026-89435 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-89435 being exploited in the wild.

**How severe is CVE-2026-89435?** High severity, with a CVSS score of 8.8, published 30 October 2026.

**Which products and versions are affected?** Formidable Forms up to and including 6.35.

**Is there a fix for CVE-2026-89435?** 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-2026-89435 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-89435?** Check whether you run Formidable Forms 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 vulnerability exists in the validate_url_is_in_s3_bucket() function due to insufficient URL prefix validation on the 'file_url' parameter. The affected REST API endpoint uses a permission callback that checks only for the frm_view_forms capability—which any subscriber-level user can obtain—rather than enforcing install_plugins or activate_plugins capabilities. Authenticated attackers can exploit this to install arbitrary plugins when Formidable Pro is not installed.

## Affected products

- Formidable Formidable Forms up to and including 6.35

## Timeline

- 2026-10-30: disclosed

## References

- [https://plugins.trac.wordpress.org/browser/formidable/tags/6.35/classes/controllers/FrmAddonsController.php](https://plugins.trac.wordpress.org/browser/formidable/tags/6.35/classes/controllers/FrmAddonsController.php)
- [https://plugins.trac.wordpress.org/browser/formidable/tags/6.35/classes/controllers/FrmAddonsController.php](https://plugins.trac.wordpress.org/browser/formidable/tags/6.35/classes/controllers/FrmAddonsController.php)

## Related threats

- [Formidable Forms unauthenticated payment gateway rate limit bypass](https://junglewise.ai/threats/cve-2026-85642-the-formidable-forms-wordpress-plugin-before-7-0-does-not-verify)
- [Formidable Forms unauthenticated arbitrary shortcode execution](https://junglewise.ai/threats/cve-2026-19857-formidable-forms-unauthenticated-arbitrary-shortcode-execution)
- [Formidable Forms Stored Cross-Site Scripting via frm_user_id parameter](https://junglewise.ai/threats/cve-2026-18331-formidable-forms-stored-cross-site-scripting-via-frm-user-id)