This indicates an attack attempt to exploit a Remote Code Execution vulnerability in Microsoft Internet Explorer.
The vulnerability is due to insufficient sanitizing of user supplied inputs in the application. An attacker can trick an unsuspecting user into visiting a malicious webpage and execute arbitrary script code within the context of the target's browser.
Internet Explorer 9
Internet Explorer 8
Internet Explorer 7
Internet Explorer 6
System Compromise: Remote attackers can execute arbitrary script code within the context of the target user's browser.
Apply the most recent upgrade or patch from the vendor.