upgrade.py in the hp-upgrade service in HP Linux Imaging and Printing (HPLIP) 3.x through 3.13.11 launches a program from an http URL, which allows man-in-the-middle attackers to execute arbitrary code by gaining control over the client-server data stream.
http://www.ubuntu.com/usn/USN-2085-1
http://www.debian.org/security/2013/dsa-2829
http://openwall.com/lists/oss-security/2013/12/05/2
http://lists.opensuse.org/opensuse-updates/2014-01/msg00087.html