Mozilla Firefox 2.x before 2.0.0.18, Thunderbird 2.x before 2.0.0.18, and SeaMonkey 1.x before 1.1.13 do not properly change the source URI when processing a canvas element and an HTTP redirect, which allows remote attackers to bypass the same origin policy and access arbitrary images that are not directly accessible to the attacker.  NOTE: this issue can be leveraged to enumerate software on the client by performing redirections related to moz-icon.