Use-after-free vulnerability in the browser engine in Mozilla Firefox before 3.6.28 and 4.x through 10.0, Firefox ESR 10.x before 10.0.3, Thunderbird before 3.1.20 and 5.0 through 10.0, Thunderbird ESR 10.x before 10.0.3, and SeaMonkey before 2.8 allows remote attackers to execute arbitrary code via vectors involving an empty argument to the array.join function in conjunction with the triggering of garbage collection.