(Sorry for the cross post but felt this was important enough to get a bit of a wider audience.)
For anyone who takes system security seriously please be aware of a local root exploit for current version of calibre
Proof of concept exploit:
http://www.exploit-db.com/exploits/18071/
Details
https://bugs.launchpad.net/calibre/+bug/885027
Everyone should make sure they update their software as soon as an update with patches is released.