Debian Security Advisory 662-2 – Andrew Archibald discovered that the last update to squirrelmail which was intended to fix several problems caused a regression which got exposed when the user hits a session timeout.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/36628/dsa-662-2.txt
Source: https://packetstormsecurity.com/files/36628/Debian-Linux-Security-Advisory-662-2.html