(Pwn2Own) Microsoft Windows xxxEndDeferWindowPosEx Window Use-After-Free Privilege Escalation Vulnerability

This vulnerability allows local attackers to execute arbitrary code on vulnerable installations of Microsoft Windows. User interaction is required to exploit this vulnerability in that the target must visit a malicious page or open a malicious file. The specific flaw exists within the handling of Window objects. The issue lies in the failure to increment a reference counter prior to calling userland code. An attacker can leverage this vulnerability to escalate privileges and execute code within the context of SYSTEM.