CVE-2025-62659 identifies a Cross-Site Scripting (XSS) vulnerability classified under CWE-79 in the MediaWiki CookieConsent extension maintained by The Wikimedia Foundation. This vulnerability exists in versions from v0.1.0 up to but not including v2.0.0. The root cause is improper neutralization of user-supplied input during the generation of web pages, which allows an attacker to inject malicious JavaScript code into pages rendered by the extension. When a victim user visits a compromised page, the injected script can execute in their browser context, potentially leading to session hijacking, cookie theft, or redirection to malicious sites. The CVSS 4.0 vector indicates network attack vector (AV:N), low attack complexity (AC:L), requiring privileges (PR:L) and user interaction (UI:P), with low impact on confidentiality and integrity but no impact on availability. The vulnerability does not require authentication but does require some privileges and user interaction, limiting its exploitability. No public exploits have been reported, and no patches are currently linked, suggesting the fix is forthcoming or under development. The vulnerability affects only the CookieConsent extension, not the core MediaWiki software, but given MediaWiki's widespread use in public and private sectors, the risk remains relevant. The issue was reserved and published in October 2025, indicating recent discovery.

For European organizations, the primary impact of this vulnerability is the potential compromise of user sessions and data confidentiality through XSS attacks. Organizations using MediaWiki with the vulnerable CookieConsent extension may face targeted attacks aiming to steal authentication tokens or perform phishing via script injection. This can undermine trust in public-facing wikis or internal knowledge bases, especially in government, educational institutions, and enterprises relying on MediaWiki for documentation and collaboration. Although the CVSS score is low, the presence of privileges and user interaction requirements means attackers might exploit insider threats or social engineering to trigger the vulnerability. The impact on data integrity and availability is minimal, but confidentiality breaches could lead to secondary attacks or data leakage. Given the widespread use of MediaWiki in Europe, particularly in countries with strong open data and transparency initiatives, the threat could affect sensitive public information portals. However, the lack of known exploits and the limited scope of the extension reduce immediate risk.

To mitigate this vulnerability, European organizations should prioritize upgrading the MediaWiki CookieConsent extension to version 2.0.0 or later once it is released, as this will contain the necessary input validation and output encoding fixes. Until the patch is available, administrators should consider disabling the CookieConsent extension if feasible or restricting its use to trusted user groups to minimize exposure. Implementing Content Security Policy (CSP) headers can help reduce the impact of potential XSS by restricting script execution sources. Additionally, organizations should audit their MediaWiki configurations to ensure minimal privileges are granted to users interacting with the extension and educate users about the risks of clicking suspicious links or interacting with untrusted content. Regular security reviews and monitoring for unusual activity in MediaWiki logs can help detect exploitation attempts early. Finally, coordinating with Wikimedia Foundation announcements and security advisories will ensure timely updates.