Overview
This article details CVE-2025-65186, a stored Cross-Site Scripting (XSS) vulnerability affecting Grav CMS version 1.7.49. This vulnerability allows authenticated users with page editing privileges to inject malicious JavaScript code into page content via the Markdown editor. When other users, particularly administrators, view the affected page in the Grav CMS admin interface, the injected script executes, potentially leading to account compromise, data theft, or other malicious activities.
Technical Details
The vulnerability lies in the inadequate sanitization of user-supplied input within the page editor’s Markdown functionality. Specifically, the application fails to properly escape or remove <script> tags. An attacker can craft a page containing a malicious <script> tag within the Markdown content. Upon saving the page, this script is stored in the Grav CMS database.
When an administrator or other authenticated user views the page through the admin interface, the stored script is rendered in the browser, leading to the execution of the attacker’s malicious code. This constitutes a stored XSS vulnerability, as the malicious script is persistently stored and executed on subsequent page views.
Example Payload:
<script>alert('XSS Vulnerability!');</script>CVSS Analysis
As of the publication of this article, a CVSS score is not yet available for CVE-2025-65186. However, given that it is a stored XSS vulnerability that can impact administrative users, it is likely to receive a High severity rating once a CVSS score is assigned.
Possible Impact
The successful exploitation of this vulnerability could have significant consequences, including:
- Account Compromise: An attacker could steal administrator cookies, allowing them to impersonate the administrator and gain complete control over the Grav CMS website.
- Data Theft: Sensitive data stored within the Grav CMS website could be accessed and stolen by the attacker.
- Malware Distribution: The attacker could inject malicious code that redirects users to phishing sites or downloads malware onto their computers.
- Website Defacement: The attacker could modify the website’s content to display malicious or misleading information.
Mitigation or Patch Steps
To mitigate this vulnerability, the following steps are recommended:
- Upgrade Grav CMS: Upgrade to a version of Grav CMS that includes a fix for CVE-2025-65186. Check the Grav CMS website for the latest version and release notes.
- Input Sanitization: If upgrading is not immediately possible, consider implementing custom input sanitization measures to filter out potentially malicious
<script>tags and other potentially harmful HTML elements. However, relying solely on custom sanitization can be risky and is not a substitute for a proper patch. - Web Application Firewall (WAF): Employing a Web Application Firewall (WAF) can provide an additional layer of protection by filtering out malicious requests before they reach the Grav CMS application.
- Restrict Page Editing Permissions: Limit page editing permissions to only trusted users to reduce the risk of malicious code being injected.
