Users would need to be tricked into clicking on a Web link in order to launch the malicious code, Cooper said. But once that was done, it could set up a chain of events that could ultimately let a hacker gain control of the user's system, he said.
All users of Internet Explorer version 5.5 and 6.x are affected by the vulnerability, Computer Terrorism said.
The problem is serious enough that Cooper believes that Microsoft will patch Internet Explorer in advance of its next monthly security update, which is scheduled to occur Dec. 13. "I would expect Microsoft to go into emergency patch mode and push something out very quickly," he said.
No one at Microsoft was available for immediate comment on the issue.