Collabora Online is a collaborative online office suite. A reflected XSS vulnerability was found in Collabora Online prior to version 6.4.9-5. An attacker could inject unescaped HTML into a variable as they created the Collabora Online iframe, and execute scripts inside the context of the Collabora Online iframe. This would give access to a small set of user settings stored in the browser, as well as the session's authentication token which was also passed in at iframe creation time. The issue is patched in Collabora Online 6.4.9-5. Collabora Online 4.2 is not affected.