CVE-2025-2594 is a high-severity vulnerability affecting the User Registration & Membership WordPress plugin versions prior to 4.1.3, specifically when the Membership Addon is enabled. The vulnerability arises from improper validation of user-supplied data in an AJAX action. This flaw allows an attacker to bypass authorization controls by manipulating the user ID parameter, effectively authenticating as any user on the target WordPress site, including administrators. The core issue is classified under CWE-639 (Authorization Bypass Through User-Controlled Key), indicating that the system trusts user-controlled input to grant access without proper verification. Exploitation requires no prior authentication or user interaction, and the attack vector is remote over the network. The CVSS v3.1 base score is 8.1, reflecting high impact on confidentiality, integrity, and availability. Successful exploitation grants full administrative privileges, enabling attackers to modify site content, steal sensitive data, install backdoors, or disrupt services. Although no known exploits are currently reported in the wild, the simplicity of the attack vector and the critical privileges gained make this a significant threat to WordPress sites using this plugin. The absence of a patch link indicates that remediation may still be pending or not widely distributed at the time of reporting.

For European organizations relying on WordPress websites with the User Registration & Membership plugin and its Membership Addon, this vulnerability poses a severe risk. Attackers could gain unauthorized administrative access, leading to data breaches involving personal data protected under GDPR, defacement of websites, disruption of business operations, and potential spread of malware or ransomware. Given the widespread use of WordPress in Europe for corporate, governmental, and e-commerce sites, exploitation could undermine trust and cause regulatory penalties. The ability to authenticate as any user without credentials also increases the risk of lateral movement within networks if the compromised WordPress instance is integrated with internal systems. The high severity and ease of exploitation make timely mitigation critical to prevent significant operational and reputational damage.

European organizations should immediately verify if their WordPress installations use the User Registration & Membership plugin with the Membership Addon enabled. If so, they must upgrade to version 4.1.3 or later once available. Until a patch is applied, organizations should consider disabling the Membership Addon or the plugin entirely to eliminate the attack surface. Implementing Web Application Firewalls (WAFs) with custom rules to detect and block suspicious AJAX requests containing user ID parameters can provide temporary protection. Additionally, monitoring logs for unusual authentication patterns or access attempts targeting AJAX endpoints is recommended. Organizations should also enforce strict access controls on administrative interfaces and consider multi-factor authentication to reduce the impact of compromised credentials. Regular security audits and vulnerability scanning focused on WordPress plugins can help detect similar issues proactively.