Mozilla: Memory corruption found using Address Sanitizer (MFSA 2013-48)

The gfxSkipCharsIterator::SetOffsets function in Mozilla Firefox before 21.0, Firefox ESR 17.x before 17.0.6, Thunderbird before 17.0.6, and Thunderbird ESR 17.x before 17.0.6 allows remote attackers to execute arbitrary code or cause a denial of service out-of-bounds read via unspecified vectors...