CVE-2026-13598 Overview
CVE-2026-13598 is a broken access control vulnerability in the RestrictMate WordPress plugin versions before 1.3.0. The plugin fails to restrict the user role parameter supplied during account registration. Unauthenticated attackers can submit a registration request specifying the administrator role and receive a logged-in administrator session in response. Successful exploitation results in full site takeover, including the ability to install malicious plugins, modify content, exfiltrate user data, and pivot to underlying hosting infrastructure. The flaw requires no authentication, no user interaction, and can be triggered remotely against any site running the vulnerable plugin with registration enabled.
Critical Impact
Unauthenticated attackers can create administrator accounts and take over any WordPress site running RestrictMate before version 1.3.0.
Affected Products
- RestrictMate WordPress plugin versions prior to 1.3.0
- WordPress sites with the vulnerable plugin installed and registration enabled
- Any hosting environment where the affected plugin is active
Discovery Timeline
- 2026-08-23 - CVE-2026-13598 published to NVD
- 2026-08-26 - Last updated in NVD database
Technical Details for CVE-2026-13598
Vulnerability Analysis
The vulnerability is a broken access control flaw in the plugin's registration handler. RestrictMate accepts a client-supplied user role parameter during account creation without validating it against an allow list. The registration workflow processes the submitted role and assigns it directly to the newly created account. Attackers can therefore self-provision an administrator account through a normal registration request. The plugin also returns an authenticated session for the newly created user, removing any need for a follow-up login step. This class of flaw maps to CWE-269 (Improper Privilege Management) and CWE-862 (Missing Authorization) in registration logic.
Root Cause
The root cause is the absence of server-side validation on the role field submitted during registration. Secure WordPress registration flows must ignore client-supplied role parameters and force the default role defined in wp_options (typically subscriber). RestrictMate instead trusts the incoming value and passes it to wp_insert_user() or an equivalent path, allowing arbitrary role assignment.
Attack Vector
Exploitation requires a single unauthenticated HTTP POST request to the plugin's registration endpoint with the role parameter set to administrator. The server responds with a valid authentication cookie for the new administrator account. From that point, the attacker can install backdoor plugins, edit theme PHP files to achieve code execution, or extract database credentials from wp-config.php through a file editor. No brute force, phishing, or existing credentials are required.
For a detailed technical breakdown, refer to the WPScan Vulnerability Analysis.
Detection Methods for CVE-2026-13598
Indicators of Compromise
- Unexpected user accounts with the administrator role in wp_users and wp_usermeta tables, especially with recent user_registered timestamps.
- Registration POST requests to the plugin endpoint containing a role=administrator parameter in access logs.
- New plugin or theme uploads shortly after an unfamiliar administrator account is created.
- Modifications to wp-config.php, .htaccess, or theme files (functions.php) originating from the session of a newly created account.
Detection Strategies
- Query the WordPress database for administrator accounts created after the plugin was installed and cross-reference against a known-good list.
- Inspect web server access logs for POST requests to registration endpoints where the request body includes a role field.
- Monitor for authentication cookies issued immediately after a registration request from the same client IP.
Monitoring Recommendations
- Ingest WordPress audit logs and web server logs into a centralized log platform and alert on privileged user creation events.
- Alert on any plugin installation, theme editor use, or wp-config.php read attempt performed by an account less than 24 hours old.
- Track anomalous outbound connections from the WordPress host following administrator account creation.
How to Mitigate CVE-2026-13598
Immediate Actions Required
- Update the RestrictMate plugin to version 1.3.0 or later on every affected WordPress site.
- Audit the wp_users table and remove any unauthorized administrator accounts, then rotate credentials for all remaining privileged users.
- Rotate WordPress secret keys and salts in wp-config.php to invalidate any hijacked sessions.
- Review installed plugins, themes, and scheduled tasks (wp_options cron entries) for backdoors added during the exposure window.
Patch Information
The vendor addressed the flaw in RestrictMate 1.3.0 by enforcing server-side role validation during registration. Site owners should upgrade through the WordPress plugin management console or by replacing the plugin directory with the patched release. See the WPScan Vulnerability Analysis for confirmation of the fixed version.
Workarounds
- Deactivate and remove the RestrictMate plugin until the patched version can be deployed.
- Disable open user registration by unchecking Anyone can register under Settings > General in WordPress.
- Deploy a web application firewall rule that blocks registration requests containing a role parameter with a value other than subscriber.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
