Late on Friday, May 3, 2013, Microsoft published a Security Advisory (2847140) to communicate that they are investigating a vulnerability in Internet Explorer 8. Interesting enough, IE6, IE7, IE9, and IE10 are not vulnerable to this newly reported flaw.
Per the security advisory:
This is a remote code execution vulnerability. The vulnerability exists in the way that Internet Explorer accesses an object in memory that has been deleted or has not been properly allocated. The vulnerability may corrupt memory in a way that could allow an attacker to execute arbitrary code in the context of the current user within Internet Explorer. An attacker could host a specially crafted website that is designed to exploit this vulnerability through Internet Explorer and then convince a user to view the website.
Read the full advisory: Microsoft Security Advisory (2847140)