Heap-based buffer overflow in Windows Live Messenger 8.0 allows user-assisted attackers to execute arbitrary code via a crafted Contact List (.ctt) file, which triggers the overflow when it is imported by the user.
https://exchange.xforce.ibmcloud.com/vulnerabilities/27417
http://www.securityfocus.com/archive/1/438442/100/0/threaded
http://securitydot.net/xpl/exploits/vulnerabilities/articles/1108/exploit.html