Microsoft is investigating the public report of a data-stealing vulnerability impacting its newest web browser, Internet Explorer (IE) 8.
In a post Friday to the Full Disclosure mailing list, Google security engineer Chris Evans described the issue as a "nasty vulnerability" that could be exploited to allow an arbitrary website to force a user to post a message on a social networking site such as Twitter. Attackers also could leverage the bug to hijack data from a victim's computer.
Evans first revealed the flaw in December. In a blog post then, he said the bug could permit cross-domain theft because of a weakness in the way browsers handle CSS style sheets.
Apple, Google, Mozilla and Opera reportedly all were once affected but have since fixed the hole.
Evans said he has tried to get Microsoft to issue a patch but thus far has been unsuccessful. He said the software giant may have known about the flaw since at least 2008, and it may affect earlier versions of IE.
Microsoft late Friday tweeted that it was aware of the issue and planned to investigate over the weekend.
Jason Miller, data and security team manager at patch management firm Shavlik Technologies, said IT administrators should await word from Microsoft before taking any action.
"As Microsoft is investigating this issue, we fully expect a security advisory to be released with this issue soon," Miller said. "Until Microsoft fully researches the issue, there are no actions that need to be taken with this issue. It is very important to wait for vendor confirmation with zero-day exploits. Security researchers that publicly disclose vulnerabilities may not have all the information."