Microsoft is aware of active attacks that leverage a vulnerability in Microsoft XML Core Services 3.0, 4.0, 5.0, and 6.0. The vulnerability could allow remote code execution if a user views a specially crafted webpage using Internet Explorer. An attacker would have no way to force users to visit such a website. Instead, an attacker would have to convince users to visit the website, typically by getting them to click a link in an email message or Instant Messenger message that takes them to the attackers website. The vulnerability affects all supported releases of Microsoft Windows, and all supported editions of Microsoft Office 2003 and Microsoft Office 2007.
via Microsoft Security Advisory 2719615: Vulnerability in Microsoft XML Core Services Could Allow Remote Code Execution.