openwebmail.pl in Open WebMail 1.7 and 1.71 reveals sensitive information in error messages and generates different responses whether a user exists or not, which allows remote attackers to identify valid usernames via brute force attacks and obtain certain configuration and version information.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2002-2388
http://www.securityfocus.com/bid/6232
http://www.iss.net/security_center/static/10684.php
http://archives.neohapsis.com/archives/bugtraq/2002-11/0278.html