Secunia Security Advisory – Debian has issued an update for webcalendar. This fixes a weakness, which can be exploited by malicious people to identify valid user accounts.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/46270/sa20108.txt
Source: https://packetstormsecurity.com/files/46270/Secunia-Security-Advisory-20108.html