Researchers have discovered a flaw in Mozilla's Firefox browser that can be exploited by attackers to take over a user's computer if they also have Internet Explorer (IE) installed.The flaw occurs when Firefox registers the firefoxurl:// URI handler, allowing an arbitrary command line argument to invoke the program, according to an advisory released today by Secunia.
The flaw can be used to execute arbitrary code when a user visits a malicious website using IE, which then opens a vulnerable Firefox, according to Secunia.
The flaw has been confirmed in Firefox version 18.104.22.168 on a fully patched Windows XP system with Service Pack 2. It was discovered by Billy (BK) Rios, Nate Mcfeeters, and Raghav "the Pope" Dube.
Secunia ranked the flaw as "highly critical," meaning it can be exploited to execute arbitrary code.
According to a post on xs-sniper.com, Rios, Mcfeters and Dube said that the flaw can be exploited when parameters that are part of firefoxurl: are passed to Firefox.exe as options, without validation.
In an advisory released today, FrSIRT ranked the flaw as "critical."
Researcher Thor Larholm detailed a proof-of-concept exploit for the flaw on his website. He later commented that Firefox URL handler was only added to the browser in version 22.214.171.124 so that it would be compatible with Vista.
A Mozilla representative could not be reached for comment.