CVE-2012-4395

Vulnerability

A cross-site scripting (XSS) vulnerability exists in ownCloud versions before 4.0.3 in the index.php file. The redirect_url parameter is not sanitized before being output, allowing injection of arbitrary HTML and JavaScript. The fix was applied in commit [3] by adding strip_tags() to the parameter.

Exploitation

An attacker can craft a malicious URL containing a redirect_url parameter with embedded script. No authentication is required; the vulnerable code is in the login page. By tricking a victim into clicking the link, the attacker's script executes in the context of the ownCloud domain.

Impact

Successful exploitation allows the attacker to execute arbitrary web script or HTML in the victim's browser, potentially leading to session hijacking, credential theft, or defacement.

Mitigation

The vulnerability is fixed in ownCloud version 4.0.3. Users should upgrade to this version or later. No workarounds are documented.