CVE-2026-57378: Advanced Forms Authorization Bypass Flaw

CVE-2026-57378 Overview

CVE-2026-57378 is a missing authorization vulnerability [CWE-862] in the Phil Kurth Advanced Forms plugin for WordPress. The flaw affects all versions up to and including 1.9.3.7. Attackers can exploit incorrectly configured access control security levels to perform unauthorized actions over the network without authentication or user interaction. The vulnerability impacts data integrity on affected WordPress sites running the plugin.

Critical Impact

Unauthenticated attackers can perform unauthorized actions against affected WordPress sites, modifying data through the Advanced Forms plugin without requiring credentials or user interaction.

Affected Products

• Phil Kurth Advanced Forms plugin for WordPress
• All versions from initial release through 1.9.3.7
• WordPress sites with the advanced-forms plugin installed and active

Discovery Timeline

• 2026-07-13 - CVE-2026-57378 published to NVD
• 2026-07-13 - Last updated in NVD database

Technical Details for CVE-2026-57378

Vulnerability Analysis

The vulnerability originates from broken access control in the Advanced Forms plugin. The plugin fails to properly enforce authorization checks on privileged operations. Attackers can invoke plugin functionality that should be restricted to authorized users. The issue is classified under [CWE-862] Missing Authorization.

The attack is network-accessible and requires no authentication or user interaction. The primary impact is to data integrity, allowing unauthorized modification of information handled by the plugin. Confidentiality and availability are not directly affected according to the published CVSS vector.

Root Cause

The plugin exposes one or more actions that lack a capability check or nonce verification. WordPress plugins should validate user capabilities using functions such as current_user_can() before executing privileged operations. In Advanced Forms <= 1.9.3.7, these checks are missing or incorrectly configured, allowing anonymous requests to reach protected functionality.

Attack Vector

An attacker sends crafted HTTP requests to a vulnerable WordPress site running the Advanced Forms plugin. Because the endpoints do not verify caller identity or permissions, the plugin processes the requests as if they came from an authorized user. This class of flaw is commonly exploited by targeting admin-ajax.php, admin-post.php, or REST API routes registered by the plugin. Refer to the Patchstack Vulnerability Report for additional technical details.

Detection Methods for CVE-2026-57378

Indicators of Compromise

• Unexpected modifications to form configurations, submissions, or plugin settings within Advanced Forms
• HTTP POST requests to admin-ajax.php or plugin-specific REST endpoints originating from unauthenticated sessions
• Web server access logs showing anomalous requests targeting advanced-forms action parameters
• New or altered form entries with no corresponding authenticated administrator session

Detection Strategies

• Inventory WordPress installations and identify sites running the advanced-forms plugin at version 1.9.3.7 or earlier
• Deploy web application firewall rules that flag unauthenticated requests to plugin action handlers
• Correlate WordPress audit logs with web access logs to detect actions performed without a valid session

Monitoring Recommendations

• Enable verbose logging in WordPress for plugin-initiated administrative actions
• Monitor outbound requests from the web server for signs of downstream abuse following unauthorized plugin actions
• Alert on repeated requests to Advanced Forms endpoints from a single IP within short time windows

How to Mitigate CVE-2026-57378

Immediate Actions Required

• Identify all WordPress instances with the Advanced Forms plugin installed and confirm the running version
• Update Advanced Forms to a release later than 1.9.3.7 once the vendor publishes a patched version
• Restrict access to WordPress administrative and AJAX endpoints using IP allow-listing where operationally feasible
• Review recent form submissions and plugin configuration changes for signs of unauthorized activity

Patch Information

At the time of publication, the vulnerability affects Advanced Forms up to and including 1.9.3.7. Administrators should monitor the Patchstack Vulnerability Report and the plugin's official distribution channel for a fixed release, then apply the update promptly.

Workarounds

• Deactivate and remove the Advanced Forms plugin until a patched version is available
• Deploy a web application firewall rule blocking unauthenticated requests to Advanced Forms action handlers
• Restrict /wp-admin/admin-ajax.php and REST API routes handling plugin actions to authenticated sessions via server-level rules
• Enforce least privilege on WordPress accounts to limit downstream impact of any unauthorized modifications

# Example nginx rule blocking unauthenticated access to plugin AJAX actions
location = /wp-admin/admin-ajax.php {
    if ($arg_action ~* "^advanced[_-]forms") {
        # Require a valid WordPress logged-in cookie
        if ($http_cookie !~* "wordpress_logged_in_") {
            return 403;
        }
    }
    include fastcgi_params;
    fastcgi_pass php_upstream;
}