The apt-get download command in APT before 1.0.9 does not properly validate signatures for packages, which allows remote attackers to execute arbitrary code via a crafted package.
https://euvd.enisa.europa.eu/vulnerability/EUVD-2014-0521
http://www.debian.org/security/2014/dsa-3025
http://ubuntu.com/usn/usn-2348-1