CVE-2025-58031 is a Stored Cross-site Scripting (XSS) vulnerability classified under CWE-79, affecting the Nextendweb Nextend Facebook Connect plugin up to version 3.1.19. This vulnerability arises from improper neutralization of input during web page generation, allowing malicious scripts to be stored and later executed in the context of users' browsers when they access affected pages. The vulnerability requires low privileges (PR:L) and user interaction (UI:R) to be exploited, but can be triggered remotely over the network (AV:N). The scope is changed (S:C), meaning the vulnerability can affect resources beyond the vulnerable component, potentially impacting the entire web application. The CVSS v3.1 base score is 6.5, indicating a medium severity level. The impact includes partial loss of confidentiality, integrity, and availability, as attackers can execute arbitrary scripts, potentially stealing session tokens, performing actions on behalf of users, or defacing content. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability affects websites using the Nextend Facebook Connect plugin, which integrates Facebook login functionality into WordPress sites, making it a target for attackers aiming to compromise user accounts or site integrity via stored XSS attacks.

For European organizations, this vulnerability poses a significant risk especially for those relying on WordPress sites with the Nextend Facebook Connect plugin for user authentication or social login features. Exploitation could lead to unauthorized access to user accounts, session hijacking, and potential data leakage, impacting GDPR compliance and user trust. The stored XSS can also be leveraged to deliver further attacks such as phishing or malware distribution within the affected websites. Organizations in sectors like e-commerce, government, education, and media that use this plugin to facilitate user login are particularly at risk. The compromise of user credentials or session tokens can lead to broader network infiltration or reputational damage. Additionally, the cross-site scripting vulnerability could be used to manipulate website content, undermining the integrity and availability of web services critical to business operations.

European organizations should immediately audit their WordPress installations to identify the presence of the Nextend Facebook Connect plugin and its version. Until an official patch is released, mitigation steps include: 1) Temporarily disabling or removing the plugin to eliminate the attack vector; 2) Implementing Web Application Firewall (WAF) rules to detect and block malicious payloads targeting stored XSS patterns specific to this plugin; 3) Enforcing strict Content Security Policy (CSP) headers to restrict script execution and reduce the impact of potential XSS payloads; 4) Conducting thorough input validation and output encoding on all user-supplied data within custom code or other plugins to minimize XSS risks; 5) Monitoring logs and user reports for suspicious activities indicative of exploitation attempts; 6) Educating site administrators and users about phishing risks associated with XSS attacks; 7) Preparing for prompt application of official patches once available and testing updates in staging environments before deployment.