hwk-fr Advanced Custom Fields Extended Plugin up to 0.9.2.7 on WordPress AJAX handler acf_verify_ajax acf_nonce improper authorization

Summaryinfo

A vulnerability, which was classified as critical, was found in hwk-fr Advanced Custom Fields Extended Plugin up to 0.9.2.7. This impacts the function acf_verify_ajax of the component AJAX handler. Executing a manipulation of the argument acf_nonce can lead to improper authorization. The identification of this vulnerability is CVE-2026-2839. The attack may be launched remotely. There is no exploit available.

Detailsinfo

A vulnerability classified as critical was found in hwk-fr Advanced Custom Fields Extended Plugin up to 0.9.2.7. This vulnerability affects the function acf_verify_ajax of the component AJAX handler. The manipulation of the argument acf_nonce with an unknown input leads to a improper authorization vulnerability. The CWE definition for the vulnerability is CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at wordfence.com. This vulnerability was named CVE-2026-2839 since 02/19/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. There are known technical details, but no exploit is available. The current price for an exploit might be approx. USD $0-$5k (estimation calculated on 10/28/2026). The MITRE ATT&CK project declares the attack technique as T1548.002.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Type

• WordPress Plugin

Vendor

• hwk-fr

Name

• Advanced Custom Fields Extended Plugin

Version

• 0.9.2.0
• 0.9.2.1
• 0.9.2.2
• 0.9.2.3
• 0.9.2.4
• 0.9.2.5
• 0.9.2.6
• 0.9.2.7

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