Hackers have discovered a vulnerability in Microsoft's popular IE (Internet Explorer) browser, and have released code that could be used to attack users of the program.
The vulnerability is similar to a bug that Microsoft patched last month in a multimedia component of IE, according to Vincent Hwang, group product manager with Symantec's security response team.
Though a sample exploit of the vulnerability was posted on Wednesday by hackers on the xsec.org website, Symantec has yet to see the code used in any attacks, according to Hwang.
To take advantage of the exploit code, attackers would first need to trick users into viewing a maliciously encoded web page. They could then run unauthorised code on a victim's computer.
It is unclear right now which versions of Windows and IE are affected by the vulnerability. Researchers at Secunia said they were able to create a "fully working" exploit for the latest version of Windows XP running IE 6.0. Windows 2000 users are also vulnerable, Secunia said.
Microsoft security researchers were unavailable to comment on the issue, but a spokesman for the company's public relations agency said the matter was under investigation.
Symantec calls the bug 'critical', and Secunia rates the issue as 'highly critical', its most severe rating. The Secunia alert can be found here.