CVE-2026-12349: KingComposer Auth Bypass Vulnerability

CVE-2026-12349 Overview

CVE-2026-12349 affects the Premium Addons for KingComposer plugin for WordPress in all versions up to and including 1.1.1. The vulnerability stems from missing authorization and capability checks on the add_custom_sidebar() and remove_custom_sidebar() AJAX handlers. Both handlers are exposed through wp_ajax_nopriv_* hooks and write directly to the octagon_custom_sidebar option via update_option(). Unauthenticated attackers can create arbitrary custom widget areas or delete existing custom sidebars. Widgets assigned to affected areas silently lose their registration and stop rendering. The issue is classified as Missing Authorization [CWE-862].

Critical Impact
Unauthenticated remote attackers can modify or delete custom widget areas, causing site widgets to silently stop rendering and degrading front-end functionality.

Affected Products

Premium Addons for KingComposer plugin for WordPress
All versions up to and including 1.1.1
WordPress sites exposing the plugin's AJAX endpoints

Discovery Timeline

2026-06-30 - CVE-2026-12349 published to NVD
2026-07-01 - Last updated in NVD database

Technical Details for CVE-2026-12349

Vulnerability Analysis

The Premium Addons for KingComposer plugin registers two AJAX handlers, add_custom_sidebar() and remove_custom_sidebar(), on both authenticated and unauthenticated hooks. Registration on wp_ajax_nopriv_* exposes these handlers to any anonymous visitor. Neither handler performs a capability check with current_user_can(), and neither validates a nonce with check_ajax_referer().

Both handlers write to the persistent octagon_custom_sidebar option using update_option(). An attacker can add arbitrary entries to the sidebar registry or remove legitimate entries. When a registered sidebar is removed, widgets previously assigned to that area lose their binding and stop rendering on the front end.

The impact is limited to integrity of the plugin's sidebar configuration data. There is no direct information disclosure or code execution path, but repeated abuse can disrupt site presentation and administrative workflows.

Root Cause

The root cause is a Missing Authorization flaw [CWE-862]. The plugin author registered privileged administrative actions on public, unauthenticated AJAX endpoints without adding capability or nonce verification.

Attack Vector

An unauthenticated attacker sends crafted POST requests to wp-admin/admin-ajax.php with the action parameter set to the vulnerable handler names. Because the endpoints are network-reachable and require no authentication or user interaction, exploitation can be automated at scale against any site running a vulnerable version. Technical details for the affected code paths are documented in the WordPress Plugin Code Review and the Wordfence Vulnerability Report.

Detection Methods for CVE-2026-12349

Indicators of Compromise

Unexpected entries in the octagon_custom_sidebar WordPress option value
Front-end pages missing widgets that previously rendered in custom sidebar areas
POST requests to /wp-admin/admin-ajax.php with action=add_custom_sidebar or action=remove_custom_sidebar from unauthenticated sessions
Absence of a valid WordPress authentication cookie on requests hitting these handlers

Detection Strategies

Inspect web server access logs for anonymous POST requests targeting admin-ajax.php with the vulnerable action values
Compare the current octagon_custom_sidebar option contents against a known-good backup
Alert on high-frequency admin-ajax.php traffic without valid wordpress_logged_in_* cookies

Monitoring Recommendations

Enable WordPress audit logging to capture changes to plugin options and widget assignments
Forward web access logs and WordPress application logs to a centralized SIEM for correlation
Track sudden drops in widget-rendered content as a functional indicator of tampering

How to Mitigate CVE-2026-12349

Immediate Actions Required

Update the Premium Addons for KingComposer plugin to a version later than 1.1.1 once available from the vendor
If no fixed version is available, deactivate and remove the plugin from affected WordPress sites
Back up the current octagon_custom_sidebar option value so legitimate sidebar configurations can be restored after cleanup
Restrict access to /wp-admin/admin-ajax.php from untrusted networks where feasible

Patch Information

At the time of NVD publication on 2026-06-30, all versions up to and including 1.1.1 are affected. Refer to the Wordfence Vulnerability Report for updated fix status and vendor guidance.

Workarounds

Deploy a Web Application Firewall (WAF) rule that blocks unauthenticated POST requests to admin-ajax.php where action equals add_custom_sidebar or remove_custom_sidebar
Remove the wp_ajax_nopriv_add_custom_sidebar and wp_ajax_nopriv_remove_custom_sidebar hook registrations via a custom mu-plugin until a vendor patch is applied
Limit which IP ranges can reach wp-admin/ paths at the reverse proxy layer

bash

# Example nginx snippet to block the vulnerable AJAX actions
location = /wp-admin/admin-ajax.php {
    if ($request_method = POST) {
        if ($args ~* "action=(add|remove)_custom_sidebar") {
            return 403;
        }
    }
}