Use-after-free vulnerability in Microsoft Internet Explorer 9 through 11 allows remote attackers to execute arbitrary code and bypass a sandbox protection mechanism via unspecified vectors, as demonstrated by VUPEN during a Pwn2Own competition at CanSecWest 2014.
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2014/ms14-037
http://www.securitytracker.com/id/1030532
http://www.securityfocus.com/archive/1/532797/100/0/threaded
http://www.pwn2own.com/2014/03/pwn2own-results-for-wednesday-day-one/