CVE 2008-5024
Mozilla Firefox 3.x before 3.0.4, 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 escape quote characters used for XML processing, which allows remote attackers to conduct XML injection attacks via the default namespace in an E4X document.
See the 
CVE page on Mitre.org
for more details.
