There is a new bug in Netscape Communicator 4.07 (Win95), 4.05 (WinNT 4.0) (probably others) which allows reading the user's cache (including the info in GET forms). This info may be sent to an arbitrary host, even if the user is behind firewall.
Part of the code is borrowed from Dan Brumleve (nothing@shout.net).
Workaround: Disable Javascript.

Cick here for a demonstration of the "cache reading" bug