Firefox before 1.0.5 and Mozilla before 1.7.9 does not properly clone base objects, which allows remote attackers to execute arbitrary code by navigating the prototype chain to reach a privileged object.
Exploitability
AV:NAC:LAu:NImpact
C:PI:PA:P7.5/AV:N/AC:L/Au:N/C:P/I:P/A:P