CVE-2025-50051 is a stored Cross-site Scripting (XSS) vulnerability affecting the WP-Members plugin developed by Chad Butler, specifically versions up to 3.5.4. This vulnerability arises from improper neutralization of user-supplied input during web page generation, classified under CWE-79. Stored XSS occurs when malicious input is saved by the application and later rendered in a web page without proper sanitization or encoding, allowing an attacker to execute arbitrary JavaScript in the context of other users' browsers. The CVSS 3.1 base score is 6.5 (medium severity), with vector AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L, indicating that the vulnerability can be exploited remotely over the network with low attack complexity, requires low privileges (authenticated user), and user interaction (UI:R) is necessary. The scope is changed (S:C), meaning the vulnerability affects components beyond the initially vulnerable component, and it impacts confidentiality, integrity, and availability to a limited extent (low impact on each). No known exploits are currently reported in the wild, and no patches have been published yet. The vulnerability allows an attacker with authenticated access to inject malicious scripts that can execute in the browsers of other users viewing the affected pages, potentially leading to session hijacking, privilege escalation, or distribution of malware. Since WP-Members is a WordPress plugin used to manage membership and restrict content access, this vulnerability can be particularly dangerous in environments where sensitive or private data is protected behind membership controls.

For European organizations, the impact of this vulnerability can be significant, especially for those relying on WP-Members to manage user access and protect sensitive content on their WordPress sites. Exploitation could lead to unauthorized disclosure of personal data, session hijacking, or manipulation of user interactions, which may violate GDPR requirements concerning data protection and user consent. The stored XSS could be leveraged to target administrators or privileged users, potentially allowing attackers to escalate privileges or implant persistent malicious code. This can disrupt business operations, damage reputation, and lead to regulatory penalties. Organizations in sectors such as finance, healthcare, education, and government, which often use membership-based portals, are at higher risk. Additionally, the scope change in the vulnerability means that the impact could extend beyond the plugin itself, affecting other integrated components or services. The requirement for authenticated access limits exploitation to users with some level of trust, but this does not eliminate risk, as insider threats or compromised accounts could be used. The need for user interaction means social engineering or phishing may be part of the attack chain, increasing the complexity but not preventing exploitation.

1. Immediate mitigation should include restricting or closely monitoring user accounts with membership privileges to reduce the risk of malicious input submission. 2. Implement strict input validation and output encoding on all user-generated content fields within WP-Members, especially those that are rendered in web pages. 3. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts in browsers. 4. Use Web Application Firewalls (WAFs) with custom rules to detect and block typical XSS payloads targeting WP-Members plugin endpoints. 5. Regularly audit membership and user-generated content for suspicious scripts or anomalies. 6. Educate users and administrators about phishing and social engineering risks to reduce the chance of malicious user interaction. 7. Monitor official channels for patches or updates from Chad Butler and apply them promptly once available. 8. Consider temporarily disabling or replacing WP-Members if the risk is unacceptable and no patch is available. 9. For organizations with development capabilities, review and patch the plugin source code to sanitize inputs and encode outputs properly as an interim fix. 10. Log and analyze web server and application logs for unusual activity related to membership functions to detect exploitation attempts early.