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Vulnerability · Published May 28, 2026 · Assigned by Wordfence

CVE-2026-8809Advanced Custom Fields: Extended <= 0.9.2.5 - Unauthenticated Privilege Escalation via Validation Bypass to '_acf_post_id' Parameter

Critical 9.8

In plain English

A critical-severity privilege mismanagement in Advanced Custom Fields: Extended from hwk-fr. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 57% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code.

Severity (CVSS 3.1)9.8Critical
Exploit odds (30 days)0.8%top 43.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack tooling1Public PoC

Official description

The Advanced Custom Fields: Extended plugin for WordPress is vulnerable to Privilege Escalation via Validation Bypass in all versions up to and including 0.9.2.5. The vulnerability exists due to the after_validate_save_post() function unconditionally trusting the attacker-controlled _acf_post_id POST parameter — with no authentication or integrity verification — to select a cleanup branch that silently discards all validation errors not prefixed with acfe:. This makes it possible for unauthenticated attackers to suppress both the role allow-list validation error added by acfe_field_user_roles::validate_front_value() and the administrator-role capability guard error added by acfe_module_form_action_user::validate_action(), causing wp_insert_user() to execute with an attacker-supplied administrator role argument and resulting in the creation of a new administrator-level user account. Exploitation requires the target site to expose a public ACFE frontend form configured with a Create User action that maps a role field.

Affected products (as reported)

VendorProductVersions
hwk-fr Advanced Custom Fields: Extended 0 – through 0.9.2.5

Weakness: CWE-269 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References