CVE-2025-62670 is a stored Cross-Site Scripting (XSS) vulnerability identified in the FlexDiagrams Extension of the Mediawiki platform maintained by the Wikimedia Foundation. The vulnerability stems from improper neutralization of user-supplied input during the generation of web pages, specifically within the FlexDiagrams Extension's handling of diagram data. This flaw allows an attacker to inject malicious JavaScript code that is stored persistently and executed in the browsers of users who view the affected pages. The vulnerability affects the master branch of the extension, indicating it is present in the latest development version. 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) reflects that the attack can be performed remotely over the network without any authentication or user interaction, and the impact on confidentiality, integrity, and availability is low to limited but still significant. Stored XSS can be leveraged to hijack user sessions, steal cookies, perform unauthorized actions on behalf of users, or deliver further malware payloads. Although no public exploits have been reported, the presence of this vulnerability in a widely used wiki platform extension poses a risk to organizations relying on Mediawiki for collaborative knowledge management. The lack of an official patch link suggests that remediation is pending or must be implemented by administrators through configuration or code review. Given the nature of Mediawiki as a platform for public and internal knowledge bases, exploitation could undermine trust and compromise sensitive information.

For European organizations, the impact of CVE-2025-62670 can be significant, particularly for government agencies, educational institutions, and enterprises that use Mediawiki with the FlexDiagrams Extension for documentation, collaboration, or public information portals. Successful exploitation could lead to session hijacking, allowing attackers to impersonate legitimate users and access restricted content or administrative functions. This may result in unauthorized data disclosure, modification of critical documentation, or disruption of collaborative workflows. The stored XSS nature means that once malicious code is injected, it can affect all users accessing the compromised pages, amplifying the potential damage. Additionally, reputational harm and loss of user trust could arise if public-facing wikis are compromised. Although the CVSS score is medium, the ease of exploitation without authentication and user interaction increases the risk profile. The vulnerability could also be chained with other attacks to escalate privileges or move laterally within networks.

To mitigate CVE-2025-62670, European organizations should: 1) Monitor the Wikimedia Foundation and Mediawiki project repositories for official patches or updates to the FlexDiagrams Extension and apply them promptly. 2) If no patch is available, consider disabling or removing the FlexDiagrams Extension temporarily to eliminate the attack surface. 3) Implement strict input validation and sanitization on all user-supplied data related to diagram creation or editing within Mediawiki, ensuring that scripts and HTML tags are properly escaped or filtered. 4) Deploy Content Security Policy (CSP) headers tailored to Mediawiki deployments to restrict the execution of unauthorized scripts. 5) Conduct regular security audits and code reviews of custom extensions and configurations. 6) Educate users and administrators about the risks of XSS and encourage vigilance when reviewing wiki content. 7) Employ web application firewalls (WAFs) with rules targeting XSS payloads as an additional layer of defense. 8) Maintain comprehensive logging and monitoring to detect suspicious activities related to wiki content modifications.