Cross-site scripting (XSS) vulnerability in zc_install/includes/modules/pages/database_setup/header_php.php in Zen Cart 1.5.0 and earlier, when the software is being installed, allows remote attackers to inject arbitrary web script or HTML via the db_username parameter to zc_install/index.php.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.