Software Update in Apple Mac OS X 10.5.1 allows remote attackers to execute arbitrary commands via a man-in-the-middle (MITM) attack between the client and the server, using a modified distribution definition file with the "allow-external-scripts" option.
https://exchange.xforce.ibmcloud.com/vulnerabilities/39111
http://www.vupen.com/english/advisories/2007/4238
http://www.us-cert.gov/cas/techalerts/TA07-352A.html
http://www.securityfocus.com/bid/26908
http://www.securityfocus.com/archive/1/485237/100/0/threaded
http://securitytracker.com/id?1019106
http://secunia.com/advisories/28136
http://lists.apple.com/archives/security-announce/2007/Dec/msg00002.html