Use-after-free vulnerability in Microsoft Internet Explorer 9 and 10 allows remote attackers to execute arbitrary code via vectors involving crafted JavaScript code, CMarkup, and the onpropertychange attribute of a script element, as exploited in the wild in January and February 2014.
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2014/ms14-012
http://www.kb.cert.org/vuls/id/732479