Mozilla is working on patching its Firefox browser after a hacker posted details of a flaw that could let criminals run unauthorized software on a victim's machine. The flaw lies in Firefox's URL handler component, which was the source of another bug Mozilla disclosed Tuesday. This second flaw was disclosed Tuesday by Billy Rios and Nathan McFeters, security consultants with Verisign and Ernst & Young respectively.
Like the first flaw, this one could be exploited by attackers to launch programs on the victim's PC without authorization, said Tyler Reguly, a security research engineer at nCircle Network Security. "They're both related to the URL handling process," he said "It's just different errors within that handling process." Even though the code posted by Rios and McFeters can only be used to launch software that is already installed on a victim's PC, it could be very dangerous if used by criminals, Reguly said. "It's still letting you run any program that exists on the user's computer," he said. "You can make it do some fairly bad things. For example, having it use command-line FTP to download a malicious file off a server somewhere and then execute that file."