According to security company Secunia, Paul from Greyhats -- a research group -- has published details of a vulnerability that can be exploited to spoof the content of any Web site.
Using the exploit, scammers are able to manipulate all versions of IE, including Windows XP SP2 -- the latest and most secure version of the browser -- and spoof the URL and SSL signature padlock located at the bottom of the browser screen.
The vulnerability is caused by a cross-site scripting vulnerability in the DHTML Edit ActiveX control, but because the flaw is within the browser, it can be used against any Web site, Secunia said.
"That is huge," said Thomas Kristensen, chief technology officer for Secunia. "When you cross-site script a Web site, the user can’t see that anything unusual is happening. The URL looks like it's a legitimate site and if you go to the SSL padlock, it will show a certificate for the site even though it is controlled by malicious scripting."
"The malicious Web site can control what is seen in the address bar. People still don't realise the significant impact of cross-site scripting. This is the vulnerability that phishers and scammers have been looking for. You could also steal cookies from any Web site," Kristensen warned.
"The most likely outcome is a phishing email, where users click on a link, then open the browser. They then briefly see the URL of the malicious Web site, and then see the scam Web site," Kristensen added.
Nick McGrath, Microsoft's security spokesman, and the Microsoft UK security team was unavailable to comment at the time of writing because they are in the United States. The company has previously frowned upon researchers who have posted exploits without letting it know first.
Kristensen said he was unsure why Paul chose to publish the exploit before informing Microsoft. Secunia has developed an exploit test on its Web site which is available for download.
Secunia has labelled the vulnerability as "moderately critical" because people cannot use it to access systems.