Umbrel is a home server OS for self-hosting. The login functionality of Umbrel before version 1.2.2 contains a reflected cross-site scripting (XSS) vulnerability in use-auth.tsx. An attacker can specify a malicious redirect query parameter to trigger the vulnerability. If a JavaScript URL is passed to the redirect parameter the attacker provided JavaScript will be executed after the user entered their password and clicked on login. This vulnerability is fixed in 1.2.2.