Overview
A cross-site scripting (XSS) vulnerability, identified as CVE-2025-65961, has been discovered in the Contao Open Source CMS. This vulnerability allows an attacker to inject malicious code into template outputs, which is then executed in the browser of both front-end and back-end users. The vulnerability affects Contao versions prior to 4.13.57, 5.3.42, and 5.6.5. Patches are available in versions 4.13.57, 5.3.42, and 5.6.5 to address this issue.
Technical Details
CVE-2025-65961 stems from insufficient sanitization of user-controlled data within specific templates of the Contao CMS. An attacker can exploit this by injecting arbitrary HTML or JavaScript code into the template input. When the template is rendered, this injected code is executed within the user’s browser, potentially allowing the attacker to perform actions on behalf of the user, steal session cookies, or deface the website.
The vulnerability exists in how Contao handles data being rendered within certain templates. Improper escaping or sanitization allows malicious scripts to be injected and executed.
CVSS Analysis
- Severity: LOW
- CVSS Score: 3.3
- CVSS Vector: (Details would be listed here, but generally reflect low impact)
Despite the low severity score, it is important to address this vulnerability. While the impact may be limited due to the need for specific conditions for exploitation, XSS vulnerabilities can still pose a risk.
Possible Impact
Although classified as low severity, successful exploitation of CVE-2025-65961 could lead to the following:
- Cookie Theft: Attackers could potentially steal session cookies, gaining unauthorized access to user accounts.
- Website Defacement: Malicious code could be injected to alter the appearance of the website.
- Redirection: Users could be redirected to phishing sites or other malicious websites.
- Limited Privilege Escalation: In certain configurations, an attacker might be able to leverage the XSS to gain limited access to backend functionalities.
Mitigation or Patch Steps
The recommended mitigation is to upgrade your Contao CMS installation to one of the following patched versions:
- Contao 4.13.57 or later
- Contao 5.3.42 or later
- Contao 5.6.5 or later
If upgrading is not immediately possible, a workaround involves reviewing and patching the affected templates manually or avoiding their use. However, upgrading is the preferred solution.
