This vulnerability allows remote attackers to execute arbitrary code on vulnerable installations of Microsoft Internet Explorer. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The vulnerability relates to how Internet Explorer uses reference counting to manage the lifetimes of the in-memory objects representing HTML elements (CElement objects). By applying a CSS style of display:run-in to a page and performing particular manipulations, an attacker can cause an object's reference count to fall to zero prematurely, causing the object to be freed. Internet Explorer will then continue using this object after it has been freed. An attacker can leverage this vulnerability to execute code under the context of the current process.