ChurchCRM is an open-source church management system. Prior to 7.1.0, there is a Reflected Cross-Site Scripting (XSS) vulnerability on the login page, which is caused by the lack of sanitization or encoding of the username parameter received from the URL. The username parameter value is directly displayed in the login page input element without filter, allowing attackers to insert malicious JavaScript scripts. If successful, script can be executed on the client side, potentially stealing sensitive data such as session cookies or replacing the display to show the attacker's login form. This vulnerability is fixed in 7.1.0.