Microsoft Corp. warned in its second advisory this week that a flaw in its Windows operating system could let an attacker hijack a computer through the Internet Explorer web browser.

The new advisory, issued on Thursday, came only two days after the company rushed out a "critical" security update for Windows to repair a different problem that also left computers vulnerable to attacks through the browser.

"An attacker would have to host a website that contains a web page that is used to exploit this vulnerability," says the latest advisory from the world's largest software maker.

"An attacker who successfully exploited this vulnerability could gain the same user rights as the local user," including administrative control.

Flaw found in July

The flaw addressed in Microsoft's latest warning was found two months ago, but code exploiting the vulnerability was released on Wednesday, according to security research group French Security Incident Response Team (FrSIRT).

"We are not aware of any attacks attempting to use the reported vulnerability or of customer impact at this time," says Microsoft's advisory.

The software maker said it was investigating reports of the vulnerability that affects Windows 2000, Windows XP and Windows Server 2003, and said it plans to issue a fix in its next scheduled security update on Oct. 10.

The vulnerability is related to a Windows component called WebViewFolderIcon and affects the Windows Shell through the Web View function.

The company suggested several workarounds that can be used to minimize risk until the security update is released.