This indicates an attack attempt to exploit a Popups vulnerability in Microsoft Internet Explorer.
The vulnerability is located in the "Popup Window" object. A remote attacker can entice a legitimate user to access a malicious web page, which can bypass zone restrictions to inject and execute arbitrary programs.
Internet Explorer 5.01
Internet Explorer 5.5
Internet Explorer 6.0
Internet Explorer 6.0 for Windows Server 2003
System Compromise: Remote attackers can gain control of vulnerable systems.
Update to a more recent version of Internet Explorer.