CVE 2010-0178
Mozilla Firefox before 3.0.19, 3.5.x before 3.5.9, and 3.6.x before 3.6.2, and SeaMonkey before 2.0.4, does not prevent applets from interpreting mouse clicks as drag-and-drop actions, which allows remote attackers to execute arbitrary JavaScript with Chrome privileges by loading a chrome: URL and then loading a javascript: URL.
See the 
CVE page on Mitre.org
for more details.
