source: https://www.securityfocus.com/bid/10089/info

Multiple vulnerabilities have been identified in the application that may allow a remote attacker to carry out directory traversal and cross-site scripting attacks.

1st Class Mail Server version 4.01 is reported to be prone to these issues, however, it is possible that other versions are affected as well.

http://www.example.com/AUTH=[some_value]/user/list.tagz?Site=www.example.com&Mailbox=[html_code]