The vulnerability affects Internet Explorer 6 Service Pack 1 on Microsoft Windows 2000 Service Pack 4, and Internet Explorer 6, Internet Explorer 7 and Internet Explorer 8 on Windows XP, Windows Server 2003, Windows Vista, Windows Server 2008, Windows 7, and Windows Server 2008 R2.
Microsoft said that it has seen limited attempts to exploit this vulnerability in Internet Explorer 6. Security researchers unaffiliated with the company have reported the release of proof-of-concept exploit code for Internet Explorer 7 and 8.
The company said that the patch will also address vulnerabilities rated "critical" that are not under attack.
On Friday, French and German IT security organizations advised using a browser other than Internet Explorer until the vulnerability is addressed. Australian authorities have issued a similar warning.
On Wednesday, Joe Stewart, a security researcher for SecureWorks, published evidence linking China to the exploit used to attack Google, Adobe, Symantec, Juniper, Dow and Northrop Grumman, among others.
Google last week said that the attacks on its infrastructure originated from China. Stewart analyzed the malware involved in the attack and found references to a CRC (cyclic redundancy check) algorithm. That algorithm, he said in a blog post on Wednesday, "is of Chinese origin, released as part of a Chinese-language paper on optimizing CRC algorithms for use in microcontrollers."
This is evidence, he argues, that someone in the People's Republic of China created the malicious code used in the attacks.
Also on Wednesday, McAfee Labs said that it has released a variant of its Stinger antivirus software to detect and repair the "Aurora" malcode used in the attacks.