CVE-2025-65186 identifies a stored Cross Site Scripting (XSS) vulnerability in Grav CMS version 1.7.49, a popular flat-file content management system. The vulnerability arises from improper sanitization of <script> tags within the Markdown editor used by authenticated users to edit page content. Specifically, the editor fails to neutralize or remove malicious JavaScript code embedded in the page content. When an administrator or any user with access to the admin interface views the infected page, the stored XSS payload executes in their browser context. This can lead to session hijacking, privilege escalation, or unauthorized actions within the CMS. The attack vector requires the attacker to have authenticated access to the CMS to inject the payload, but no further user interaction is needed beyond viewing the compromised page. The vulnerability does not currently have a CVSS score and no public exploits have been reported. However, the flaw is significant because it targets the administrative interface, which typically has elevated privileges and access to sensitive content and configurations. The lack of proper input validation and output encoding in the Markdown editor is the root cause. This vulnerability could be leveraged by malicious insiders or attackers who have gained low-level access to the CMS to escalate their privileges or compromise the system integrity.

For European organizations using Grav CMS, this vulnerability could lead to unauthorized administrative actions, data theft, or defacement of web content. Since the XSS is stored and executes in the admin interface, attackers could hijack admin sessions, inject further malicious code, or manipulate site content and configurations. This threatens the confidentiality, integrity, and availability of the CMS-managed websites. Organizations with multiple administrators or editors are at higher risk due to increased exposure. The impact is particularly critical for sectors relying on Grav CMS for public-facing or internal portals, including government, education, and media entities in Europe. Compromise could result in reputational damage, regulatory non-compliance (e.g., GDPR breaches if personal data is exposed), and operational disruptions. The requirement for authentication limits the attack surface but does not eliminate risk, especially if credential theft or insider threats are present.

1. Apply official patches or updates from Grav CMS as soon as they become available to address this vulnerability. 2. Until patches are released, restrict page editing permissions to only highly trusted users and minimize the number of users with admin or editor roles. 3. Implement additional input validation and sanitization controls at the web application firewall (WAF) or reverse proxy level to detect and block malicious script tags in Markdown content. 4. Conduct regular audits of page content for suspicious scripts or injected code, especially in pages edited recently. 5. Enforce strong authentication mechanisms, including multi-factor authentication (MFA), to reduce the risk of credential compromise. 6. Educate administrators and editors about the risks of XSS and safe content editing practices. 7. Monitor logs and user activity for unusual behavior indicative of exploitation attempts. 8. Consider isolating the admin interface behind VPN or IP allowlists to limit access to trusted networks.