Microsofts freshly minted Internet Explorer 7 browser is vulnerable to a window injection vulnerability that has haunted earlier versions of IE since Dec. 2004, according to a warning from Secunia.
The security alerts aggregator said the flaw, which carries a "moderately critical" rating, could be exploited to spoof the content of Web sites for use in phishing and identity theft attacks.
"The problem is that a Web site can inject content into another sites window if the target name of the window is known," said Secunia, in Copenhagen, Denmark.
The company has constructed a test that shows how IE 7 can be tricked by a malicious Web site to spoof the content of a pop-up window opened on a trusted site.
Secunia said the vulnerability was confirmed on a fully patched system with Internet Explorer 7.0 and Microsoft Windows XP SP2 (Service Pack 2).
The flaw was first flagged in IE 6.0 almost two years ago. In Dec. 2004, Secunia issued an advisory for the exact bug and warned IE users to avoid browsing untrusted sites while browsing trusted sites.
The flaw remains unpatched in IE 6.0, suggesting that Microsoft may not consider it serious enough to warrant a patch.
A spokesperson for Microsoft said the company does not consider this a security vulnerability.
"[Secunia] describes a by-design behavior in popular Web browsers that allows a Web site to open or re-use a pop-up window. In Internet Explorer 7, the Web pages actual URL is displayed in a pop-up window address bar, enabling users to accurately make a trust decision," the spokesperson said.
The window injection bug is the third security issue found in IE 7 since the final version of the browser shipped on Oct. 19. On the same day the browser was released, security researchers discovered an information disclosure vulnerability that could be used in spoofing attacks but Microsoft said the problem exists in Outlook Express and is not an IE flaw.
A third issue, described as a "weakness" in the browser, could also be exploited by phishers to display a pop-up with a somewhat spoofed address bar where a number of special characters have been appended to the URL.
Exploit code for this bug is publicly available.
"This makes it possible to only display a part of the address bar, which may trick users into performing certain unintended actions," Secunia said in an alert.
Editors Note: This story was updated to include comments from a Microsoft spokesperson.
Check out eWEEK.coms for the latest security news, reviews and analysis. And for insights on security coverage around the Web, take a look at eWEEK.com Security Center Editor Larry Seltzers Weblog.