Aptdaemon 0.43 and earlier in Ubuntu 11.04, 11.10, and 12.04 LTS does not authenticate packages when the transaction is not simulated, which allows remote attackers to install arbitrary packages via a man-in-the-middle attack.
https://exchange.xforce.ibmcloud.com/vulnerabilities/74553
https://bugs.launchpad.net/ubuntu/%2Bsource/aptdaemon/%2Bbug/959131
http://www.securityfocus.com/bid/52855