Link:http://www.raymond.cc/blog/archives/2007/07/13/easily-show-the-contents-of-password-fields/
If I've forgotten the master password, I can easily view the contents
of password fields by simply entering a line of javascript below at
the address bar and hit enter.
javascript:(function(){var s,F,j,f,i; s = ""; F = document.forms;
for(j=0; j<F.length; ++j) { f = F[j]; for (i=0; i<f.length; ++i) { if
(f[i].type.toLowerCase() == "password") s += f[i].value + "\n"; } } if
(s) alert("Passwords in forms on this page:\n\n" + s); else
alert("There are no passwords in forms on this page.");})();
A dialog box will prompt and your password is shown!
Reveal Firefox Password
This method works on Internet Explorer, Firefox, Netscape and Opera.
When I get to know about this method, I felt that even Firefox master
password is rather useless. Turning off javascript will protect you
from this hack but then you might face problems viewing websites that
uses javascript.i