Two vulnerabilities were found in Mozilla Firefox that combined allow an attacker to run arbitrary code. The Mozilla Suite is only partially vulnerable. By causing a frame to navigate back to a previous javascript: url an attacker can inject script into any site. This could be used to steal cookies or sensitive data from that site, or to perform actions on behalf of that user. (Affects Firefox and the Suite). A separate vulnerability in the Firefox install confirmation dialog allows an attacker to execute arbitrary code by using a javascript: URL as the package icon. By default only the Mozilla Foundation update site is allowed to bring up this dialog, but the script injection vulnerability described above enables this to be exploited from any malicious site. The Mozilla Foundation has modified the update servers to prevent their use in this attack.
Firefox 1.04 is out and fixes these vulnerabilities.
*** This bug has been marked as a duplicate of 91859 ***