CVE-2025-13493: WordPress Plugin Auth Bypass Vulnerability

CVE-2025-13493 Overview

The Latest Registered Users plugin for WordPress contains an authorization bypass vulnerability that enables unauthenticated attackers to export sensitive user data. The vulnerability exists in all versions up to and including 1.4, and stems from missing authorization checks and nonce validation in the rnd_handle_form_submit function. This function is hooked to both admin_post_my_simple_form and admin_post_nopriv_my_simple_form actions, allowing any visitor to trigger user data exports without authentication.

Critical Impact

Unauthenticated attackers can export complete user details (excluding passwords and sensitive tokens) in CSV format, exposing usernames, email addresses, and other personal information stored in the WordPress user database.

Affected Products

• Latest Registered Users WordPress Plugin version 1.4 and earlier
• WordPress sites with the Latest Registered Users plugin installed

Discovery Timeline

• 2026-01-07 - CVE CVE-2025-13493 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2025-13493

Vulnerability Analysis

This vulnerability represents a classic Missing Authorization (CWE-862) flaw in WordPress plugin development. The rnd_handle_form_submit function processes form submissions that trigger user data exports but fails to implement two critical security controls: capability checks to verify the user has appropriate permissions, and nonce validation to prevent cross-site request forgery attacks.

The plugin registers handlers for both authenticated (admin_post_my_simple_form) and unauthenticated (admin_post_nopriv_my_simple_form) WordPress admin-post actions. Because the handler lacks authorization verification, attackers can directly invoke the export functionality by crafting requests to the WordPress admin-post.php endpoint with the appropriate action parameter.

Root Cause

The root cause is the absence of WordPress capability checks (such as current_user_can()) and nonce verification (such as wp_verify_nonce()) in the rnd_handle_form_submit function at line 246 of the plugin code. The function processes the export request unconditionally, regardless of the requester's authentication status or privileges.

Attack Vector

An unauthenticated attacker can exploit this vulnerability by sending a crafted HTTP request to the WordPress admin-post.php endpoint with the action parameter set to my_simple_form. The server processes this request without validating the caller's identity or permissions, generating and returning a CSV file containing user data including usernames, email addresses, registration dates, and other non-sensitive profile fields.

The attack can be performed remotely over the network without any prior authentication, making it trivially exploitable. The vulnerability only exposes read access to user data (confidentiality impact) and does not allow modification of data or service disruption.

Detection Methods for CVE-2025-13493

Indicators of Compromise

• Unusual HTTP POST requests to /wp-admin/admin-post.php with action=my_simple_form parameter from external IP addresses
• Web server access logs showing repeated requests to admin-post.php from unauthenticated sessions
• Unexpected CSV file downloads or data export activity in web server logs
• Access attempts to the vulnerable endpoint from known malicious IP addresses or automated scanning tools

Detection Strategies

• Monitor web application firewall (WAF) logs for requests containing the action=my_simple_form parameter targeting admin-post.php
• Implement log analysis rules to detect POST requests to WordPress admin endpoints from unauthenticated users
• Review WordPress activity logs for data export events that don't correspond to legitimate administrator actions
• Configure intrusion detection systems to alert on patterns consistent with WordPress plugin exploitation attempts

Monitoring Recommendations

• Enable detailed access logging for WordPress admin endpoints including admin-post.php
• Implement rate limiting on WordPress admin-post endpoints to detect and slow automated exploitation attempts
• Set up alerts for any CSV export activity or file downloads from the WordPress admin directory
• Monitor outbound data transfers for patterns indicating bulk user data exfiltration

How to Mitigate CVE-2025-13493

Immediate Actions Required

• Deactivate and remove the Latest Registered Users plugin immediately if version 1.4 or earlier is installed
• Audit web server logs for any previous exploitation attempts against the vulnerable endpoint
• Review user data for any signs of unauthorized access or data harvesting
• Consider notifying affected users if evidence of exploitation is discovered
• Implement a Web Application Firewall rule to block requests to admin-post.php with action=my_simple_form

Patch Information

At the time of publication, no patched version has been confirmed. Website administrators should check the WordPress Plugin Directory for updated versions that address this vulnerability. Until a patch is available, the plugin should be removed from production WordPress installations.

For additional vulnerability details, refer to the Wordfence Vulnerability Report.

Workarounds

• Remove or deactivate the Latest Registered Users plugin until a patched version is released
• Implement a WAF rule to block requests containing action=my_simple_form to admin-post.php
• Restrict access to WordPress admin endpoints at the web server level using IP allowlisting
• Consider using alternative user management plugins that have undergone security audits

# Apache .htaccess rule to block vulnerable endpoint
<FilesMatch "admin-post\.php$">
    <If "%{QUERY_STRING} =~ /action=my_simple_form/ || %{REQUEST_BODY} =~ /action=my_simple_form/">
        Require all denied
    </If>
</FilesMatch>