The host is installed with Mozilla Firefox 4.x through 13.0, Firefox ESR 10.x before 10.0.6, Thunderbird 5.0 through 13.0, Thunderbird ESR 10.x before 10.0.6, or SeaMonkey before 2.11 and is prone to a security bypass vulnerability. A flaw is present in the applications, which fail to handle crafted content. Successful exploitation could allow attackers to bypass intended XBL access restrictions.