Multiple unspecified vulnerabilities in the browser engine in Mozilla Firefox before 20.0, Firefox ESR 17.x before 17.0.5, Thunderbird before 17.0.5, Thunderbird ESR 17.x before 17.0.5, and SeaMonkey before 2.17 allow remote attackers to cause a denial of service (memory corruption and application crash) or possibly execute arbitrary code via unknown vectors.