The child frames in Mozilla Firefox before 1.5.0.10 and 2.x before 2.0.0.2, and SeaMonkey before 1.0.8 inherit the default charset from the parent window, which allows remote attackers to conduct cross-site scripting (XSS) attacks, as demonstrated using the UTF-7 character set.
Exploitability
AV:NAC:MAu:NImpact
C:PI:PA:N5.8/AV:N/AC:M/Au:N/C:P/I:P/A:N