CVE-2025-62662 is a stored Cross-site Scripting (XSS) vulnerability classified under CWE-79, found in the AdvancedSearch extension of the Mediawiki platform developed by the Wikimedia Foundation. The vulnerability stems from improper neutralization of user-supplied input during the generation of web pages, allowing malicious scripts to be stored and subsequently executed in the context of other users' browsers. This flaw affects the master branch of the AdvancedSearch extension prior to version 1.39. The vulnerability is remotely exploitable without requiring authentication or user interaction, increasing its risk profile. The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:L/SC:L/SI:L/SA:L) indicates network attack vector, low attack complexity, no privileges or user interaction needed, and impacts on confidentiality, integrity, and availability, albeit limited in scope. Stored XSS can be leveraged by attackers to steal session cookies, perform actions on behalf of users, deface content, or deliver malware. Although no known exploits are reported in the wild, the presence of this vulnerability in widely used Mediawiki deployments, especially in public and private sector environments, poses a tangible threat. The lack of an official patch link suggests that remediation may require updating to version 1.39 or later once released or applying custom input sanitization measures. The vulnerability highlights the importance of secure coding practices in web application extensions and the need for rigorous input validation and output encoding.

For European organizations, the impact of CVE-2025-62662 can be significant, especially for those relying on Mediawiki for internal knowledge bases, documentation, or public-facing information portals. Exploitation could lead to unauthorized disclosure of sensitive information through session hijacking or credential theft, undermining confidentiality. Integrity could be compromised by attackers injecting misleading or malicious content, damaging organizational reputation and trust. Availability impacts are generally limited but could occur if injected scripts disrupt normal operations or trigger denial-of-service conditions. Public sector entities, educational institutions, and research organizations in Europe often use Mediawiki extensively, making them attractive targets. Additionally, the vulnerability's ease of exploitation without authentication increases the risk of automated attacks or mass exploitation campaigns. Given the medium severity, organizations may face moderate operational disruption and reputational damage if the vulnerability is exploited. Compliance with GDPR and other data protection regulations could also be jeopardized if personal data is exposed through XSS attacks.

European organizations should take proactive steps to mitigate this vulnerability. First, monitor the Wikimedia Foundation's official channels for patches or updates to the AdvancedSearch extension and apply them promptly once available. Until an official patch is released, implement strict input validation and output encoding on all user-supplied data processed by the AdvancedSearch extension to neutralize potentially malicious scripts. Employ Content Security Policies (CSP) to restrict the execution of unauthorized scripts and reduce the impact of potential XSS payloads. Conduct thorough security testing, including automated scanning and manual code reviews, focusing on the AdvancedSearch extension's input handling. Limit the exposure of the Mediawiki instance by restricting access to trusted users or networks where feasible. Educate users about the risks of XSS and encourage vigilance against suspicious content or links. Regularly back up Mediawiki data to enable recovery in case of defacement or data corruption. Finally, consider deploying Web Application Firewalls (WAFs) with rules tailored to detect and block XSS attack patterns targeting Mediawiki.