Stack-based buffer overflow in the text-rendering functionality in Mozilla Firefox before 3.5.14 and 3.6.x before 3.6.11, Thunderbird before 3.0.9 and 3.1.x before 3.1.5, and SeaMonkey before 2.0.9 allows remote attackers to execute arbitrary code or cause a denial of service (memory corruption and application crash) via a long argument to the document.write method.