Home assistant is an open source home automation. The Home Assistant login page allows users to use their local Home Assistant credentials and log in to another website that specifies the redirect_uri and client_id parameters. Although the redirect_uri validation typically ensures that it matches the client_id and the scheme represents either http or https, Home Assistant will fetch the client_id and check for HTML tags on the page. These URLs are not subjected to the same scheme validation and thus allow for arbitrary JavaScript execution on the Home Assistant administration page via usage of javascript: scheme URIs. This Cross-site Scripting (XSS) vulnerability can be executed on the Home Assistant frontend domain, which may be used for a full takeover of the Home Assistant account and…