Format string vulnerability in PackageKit in Apple Mac OS X 10.6.x before 10.6.6 allows man-in-the-middle attackers to execute arbitrary code or cause a denial of service (application crash) via vectors related to interaction between Software Update and distribution scripts.
http://www.vupen.com/english/advisories/2011/0050
http://www.securitytracker.com/id?1024938
http://support.apple.com/kb/HT4498
http://secunia.com/advisories/42841
http://lists.apple.com/archives/security-announce/2011//Jan/msg00000.html