Pipermail in Mailman stores private mail messages with predictable filenames in a world-executable directory, which allows local users to read private mailing list archives.
http://www.securityfocus.com/bid/4538
http://www.iss.net/security_center/static/8874.php
http://sourceforge.net/tracker/?func=detail&atid=100103&aid=474616&group_id=103