CVE-2025-13540: Tiare Membership Privilege Escalation

CVE-2025-13540 Overview

The Tiare Membership plugin for WordPress contains a critical privilege escalation vulnerability that allows unauthenticated attackers to gain administrator access to affected WordPress sites. The vulnerability exists in all versions up to and including version 1.2, where the tiare_membership_init_rest_api_register function fails to properly restrict which user roles can be assigned during the registration process.

Critical Impact

Unauthenticated attackers can register accounts with administrator privileges, leading to complete site compromise including data theft, malware injection, and defacement.

Affected Products

• Tiare Membership plugin for WordPress versions up to and including 1.2
• WordPress sites utilizing the Tiare Wedding Vendor Directory Theme with the vulnerable plugin

Discovery Timeline

• 2025-11-27 - CVE-2025-13540 published to NVD
• 2025-12-01 - Last updated in NVD database

Technical Details for CVE-2025-13540

Vulnerability Analysis

This privilege escalation vulnerability (CWE-269: Improper Privilege Management) stems from a fundamental access control flaw in the plugin's REST API registration endpoint. The tiare_membership_init_rest_api_register function processes user registration requests without implementing proper validation or restrictions on the user role parameter.

When a new user registers through the plugin's REST API, the function accepts role assignments directly from user input without checking whether the requested role is appropriate for self-registration. This allows malicious actors to specify privileged roles such as administrator in their registration request, which the system then assigns without question.

The attack can be executed remotely over the network without any prior authentication, and requires no user interaction. A successful exploit grants the attacker full administrative control over the WordPress installation, including the ability to modify content, install malicious plugins, access sensitive data, and compromise other users on the system.

Root Cause

The root cause is the absence of input validation and authorization checks in the tiare_membership_init_rest_api_register function. The function should restrict registrations to non-privileged roles (such as subscriber or custom member roles) but instead allows arbitrary role assignment. This represents a failure to implement the principle of least privilege during the user registration workflow.

Attack Vector

An unauthenticated attacker can exploit this vulnerability by sending a crafted registration request to the plugin's REST API endpoint. The attacker includes the administrator role (or any other privileged role) in the request payload. Since the vulnerable function does not validate or sanitize the role parameter, the new account is created with administrative privileges.

The attack requires only network access to the target WordPress site and can be automated at scale, making it particularly dangerous for sites running the vulnerable plugin version.

Detection Methods for CVE-2025-13540

Indicators of Compromise

• Unexpected administrator accounts appearing in the WordPress user database
• New user registrations with administrator or elevated privileges that were not created by legitimate administrators
• Unusual REST API activity targeting the Tiare Membership plugin endpoints
• Authentication logs showing administrative actions from newly created or unfamiliar accounts

Detection Strategies

• Monitor WordPress user tables for new accounts with administrator or other elevated roles
• Review REST API access logs for suspicious registration requests containing role parameters
• Implement alerting on any new administrator account creation events
• Audit existing user accounts to identify any unauthorized privilege assignments

Monitoring Recommendations

• Enable comprehensive logging for WordPress REST API endpoints, particularly those related to user registration
• Configure real-time alerts for new user accounts created with administrative privileges
• Implement network-level monitoring for unusual traffic patterns targeting WordPress registration endpoints
• Review user account creation logs regularly for anomalies

How to Mitigate CVE-2025-13540

Immediate Actions Required

• Immediately audit all WordPress user accounts for unauthorized administrator or elevated privilege accounts
• Disable or remove the Tiare Membership plugin until a patched version is available
• If the plugin must remain active, implement firewall rules to restrict access to the vulnerable REST API endpoints
• Reset credentials and sessions for all legitimate administrator accounts as a precaution

Patch Information

Currently, no official patch has been confirmed for this vulnerability. Site administrators should check for updates from the plugin vendor. For detailed information about this vulnerability, refer to the Wordfence Vulnerability Report and the ThemeForest product page for the Tiare Wedding Vendor Directory Theme.

Workarounds

• Disable or deactivate the Tiare Membership plugin until a security update is available
• Implement a Web Application Firewall (WAF) rule to block or filter requests to the vulnerable REST API endpoint
• Use WordPress security plugins to restrict REST API access for unauthenticated users
• If possible, temporarily disable user registration functionality through WordPress settings

# Example: Disable REST API for unauthenticated users via .htaccess
# Add to WordPress root .htaccess file
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{REQUEST_URI} ^/wp-json/tiare [NC]
RewriteRule .* - [F,L]
</IfModule>