The issue allows remote attackers to inject arbitrary web script or HTML via various parameters to multiple scripts, including `join.php`, `search.php`, `photo search.php`, and `photo view.php`. The vulnerable parameters include `user`, `email`, `email2`, `f17 zip`, `agree`, `PATH INFO`, `st`, `f17 city`, `f17 country`, `f17 state`, `f19`, `wphoto`, `search`, `v`, and `return`.