Updated The latest versions of Internet Explorer and Firefox on Windows and (in the case of Firefox) Unix systems are vulnerable to attacks that could reveal the contents of sensitive files residing on a victim's hard drives.
The vulnerability resides in the functionality that allows the browsers to upload files to a remote server. It requires a victim to visit a booby-trapped website and enter text with certain characters in a comment interface or other input field.
Petko D. Petkov, a researcher who has investigated the vulnerability, says similar techniques could be used to reveal more sensitive files on Windows or Unix-based machines, for example C:\WINDOWS\system32\config\SAM in the former or /etc/passwd in the latter.
The vulnerability in Firefox was tested with versions 2.0 and 1.5. It is a variant of a bug that was reported on Bugzilla as early as 2000, according to Michal Zalewski, who is credited with discovering the flaw in that browser.
Petkov is believed to have first determined that IE 7 is also vulnerable. ®
A Microsoft spokesman said the company is investigating the report. Initial findings by Microsoft's security team are consistent with the report, specifically that "an attacker could gain access to user files if the location of a given file is already known" and would then have to convince the victim to enter the location of that file in a Web page.