Microsoft issued a security advisory on Monday warning about targeted attacks being launched that exploit a hole in the ActiveX control for the Snapshot Viewer in the Microsoft Access database management system.
Basically, an attacker would have to lure a victim, via a link in an e-mail or IM for instance, to a specially crafted Web page that could exploit the security hole to allow remote code execution. This would provide the attacker with as much access to and rights on the computer as the logged-in user has.
The vulnerability only affects the ActiveX control for the Snapshot Viewer for Microsoft Office Access 2000, 2002 and 2003.