CVE-2025-62668 is a vulnerability categorized under CWE-276 (Incorrect Default Permissions) found in the GrowthExperiments Extension of the Wikimedia Foundation's Mediawiki software, affecting versions before 1.39. The flaw arises from the extension assigning overly permissive default permissions to certain resources, which leads to resource leak exposure. This means that sensitive data or internal resources may be accessible to unauthorized remote attackers without requiring any authentication or user interaction. The vulnerability is exploitable over the network with low attack complexity, as indicated by the CVSS 4.0 vector (AV:N/AC:L/PR:N/UI:N). The impact includes potential unauthorized disclosure of information that could aid further attacks or compromise confidentiality. Although no public exploits are currently known, the exposure of internal resources can lead to reconnaissance and subsequent exploitation. The GrowthExperiments Extension is used to conduct A/B testing and feature rollouts within Mediawiki, and improper permission settings in this context can inadvertently expose experimental or sensitive data. The vulnerability affects the 'master' branch before the 1.39 release, implying that users running development or older versions are at risk. The issue is significant because Mediawiki is widely deployed in public and private sectors, including government, education, and knowledge bases, making the exposure of internal data a serious concern.

For European organizations, the impact of CVE-2025-62668 can be substantial, especially for those relying on Mediawiki for knowledge management, documentation, or public information portals. Unauthorized exposure of internal resources can lead to leakage of sensitive operational data, experimental feature details, or user information, undermining confidentiality and potentially enabling further targeted attacks. Public sector entities, universities, and research institutions that use Mediawiki extensively may face reputational damage and compliance issues under GDPR if personal or sensitive data is exposed. The vulnerability's network accessibility and lack of authentication requirements increase the risk of widespread scanning and exploitation attempts. While the vulnerability does not directly affect system integrity or availability, the information disclosure can facilitate more severe attacks. Given the collaborative and open nature of many Mediawiki deployments, attackers could leverage leaked data to craft phishing campaigns or social engineering attacks targeting European organizations.

European organizations should immediately audit their Mediawiki installations to determine if the GrowthExperiments Extension is in use and identify the version deployed. If affected, upgrading to version 1.39 or later where the issue is resolved is the primary mitigation. In the absence of an official patch, administrators should manually review and tighten file system and resource permissions related to the extension, ensuring that only authorized users and processes have access. Implement network-level access controls such as IP whitelisting or VPN requirements for accessing sensitive Mediawiki instances. Enable detailed logging and monitoring to detect unusual access patterns or attempts to exploit the vulnerability. Additionally, organizations should conduct internal security assessments to identify any data that may have been exposed and apply data loss prevention measures. Educating administrators about secure configuration practices for Mediawiki extensions can prevent similar issues. Finally, coordinate with Wikimedia Foundation security advisories for updates and best practices.