CVE-2025-13737 is a Cross-Site Request Forgery (CSRF) vulnerability identified in the Nextend Social Login and Register plugin for WordPress, affecting all versions up to and including 3.1.21. The vulnerability stems from missing or incorrect nonce validation in the 'unlinkUser' function, which is responsible for unlinking a user's social login account from their WordPress profile. Nonces are security tokens used to verify that a request is legitimate and initiated by an authenticated user. Without proper nonce validation, an attacker can craft a malicious request that, when executed by an authenticated administrator (e.g., by clicking a specially crafted link), causes the unlinking of social login accounts without the administrator's consent. This attack does not require the attacker to be authenticated themselves but does require the administrator to perform an action, making it a user-interaction dependent vulnerability. The impact is primarily on the integrity of user account linkage, potentially disrupting user login flows or causing administrative confusion. The vulnerability does not directly expose sensitive data or cause denial of service. No public exploits have been reported yet, and no official patches are listed at the time of publication. The CVSS 3.1 vector indicates network attack vector, low attack complexity, no privileges required, user interaction required, unchanged scope, no confidentiality impact, low integrity impact, and no availability impact, resulting in a score of 4.3 (medium severity).

For European organizations, this vulnerability can undermine the integrity of user authentication mechanisms on WordPress sites using the Nextend Social Login and Register plugin. Attackers could disrupt user experience by unlinking social login accounts, potentially leading to increased support requests, user lockouts, or administrative overhead. While it does not expose confidential data or cause service outages, the disruption to authentication workflows can affect customer trust and operational efficiency, especially for e-commerce platforms, membership sites, or services relying on social login for user convenience. Organizations with high administrative activity or multiple administrators are at greater risk, as the attack requires an administrator to be tricked into clicking a malicious link. The lack of known exploits reduces immediate risk, but the widespread use of WordPress and this plugin in Europe means the vulnerability could be targeted in phishing campaigns or social engineering attacks. Compliance with data protection regulations like GDPR may also be impacted if user account integrity is compromised, necessitating incident response and notification.

1. Monitor the Nextendweb vendor announcements and update the Nextend Social Login and Register plugin promptly once a security patch addressing CVE-2025-13737 is released. 2. Until an official patch is available, implement custom nonce validation or CSRF protection mechanisms on the 'unlinkUser' function by modifying the plugin code or using WordPress security hooks to enforce nonce checks. 3. Educate WordPress site administrators about the risks of clicking unsolicited links, especially those that could trigger administrative actions. 4. Employ web application firewalls (WAFs) with rules to detect and block suspicious CSRF attempts targeting the unlinkUser endpoint. 5. Limit the number of administrators with unlink privileges and enforce multi-factor authentication (MFA) for administrative accounts to reduce the risk of compromised credentials being exploited. 6. Regularly audit plugin usage and permissions to ensure only necessary plugins are active and up to date. 7. Use security plugins that can detect anomalous administrative actions or CSRF attempts and alert administrators in real time.