# CVE-2026-2839: Advanced Custom Fields: Extended authorization bypass in AJAX handlers

Source: https://junglewise.ai/threats/cve-2026-2839-the-advanced-custom-fields-extended-plugin-for-wordpress-is  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-28. Updated: 2026-10-28  
License: CC BY 4.0 with a link back

CVE-2026-2839 · Severity: medium · CVSS 5.3 · Published 2026-10-28

Advanced Custom Fields: Extended is a WordPress plugin that extends the popular form-building tool used by website administrators. Unauthenticated attackers can bypass authorization checks in AJAX handlers to access sensitive data including post titles and form structure details. An attacker can extract publicly exposed guest nonces to perform unauthorized actions without authentication.

Technologies: [Delicious Brains Advanced Custom Fields: Extended](https://junglewise.ai/threats/technologies/delicious-brains-advanced-custom-fields-extended). Vendors: [Delicious Brains](https://junglewise.ai/threats/vendors/delicious-brains).

## Quick answers

**Is CVE-2026-2839 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-2839 being exploited in the wild.

**How severe is CVE-2026-2839?** Medium severity, with a CVSS score of 5.3, published 28 October 2026.

**Which products and versions are affected?** Delicious Brains Advanced Custom Fields: Extended up to 0.9.2.7.

**Is there a fix for CVE-2026-2839?** Yes: fixed in 0.9.2.8 (implied; partial fix in 0.9.2.4). Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-2839 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-2839?** Check whether you run Delicious Brains Advanced Custom Fields: Extended 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.

## How to fix

- Fixed in 0.9.2.8 (implied; partial fix in 0.9.2.4)

## Technical details

Multiple AJAX handlers registered for unauthenticated users lack proper WordPress authorization checks (current_user_can), relying solely on ACF's acf_verify_ajax() nonce validation. Since ACF generates and exposes guest nonces in frontend page source, unauthenticated attackers can extract these nonces and craft requests to bypass WordPress visibility permissions. This allows unauthorized disclosure of post titles and internal Flexible Content layout structures; a partial fix was applied in 0.9.2.4.

## Affected products

- Delicious Brains Advanced Custom Fields: Extended up to 0.9.2.7

## Timeline

- 2026-10-28: disclosed

## References

- [https://plugins.trac.wordpress.org/browser/acf-extended/trunk/includes/fields/field-advanced-link.php](https://plugins.trac.wordpress.org/browser/acf-extended/trunk/includes/fields/field-advanced-link.php)
- [https://plugins.trac.wordpress.org/browser/acf-extended/trunk/includes/fields/field-advanced-link.php](https://plugins.trac.wordpress.org/browser/acf-extended/trunk/includes/fields/field-advanced-link.php)

## Related threats

- [Advanced Custom Fields: Extended sensitive information exposure via template injection](https://junglewise.ai/threats/cve-2026-110305-the-advanced-custom-fields-extended-plugin-for-wordpress-is)
- [Advanced Custom Fields Extended privilege escalation in front-end Forms](https://junglewise.ai/threats/cve-2026-94268-the-advanced-custom-fields-extended-wordpress-plugin-before-0-9-2)
- [Advanced Custom Fields: Extended unauthenticated RCE in post update](https://junglewise.ai/threats/cve-2026-94267-the-advanced-custom-fields-extended-wordpress-plugin-before-0-9-2)
- [Advanced Custom Fields: Extended XSS in form shortcode attributes](https://junglewise.ai/threats/cve-2026-94264-the-advanced-custom-fields-extended-wordpress-plugin-before-0-9-2)
- [Advanced Custom Fields: Extended account takeover in user update](https://junglewise.ai/threats/cve-2026-94262-the-advanced-custom-fields-extended-wordpress-plugin-before-0-9-2)