Mozilla Firefox 3.x before 3.0.6 does not properly implement the (1) no-store and (2) no-cache Cache-Control directives, which allows local users to obtain sensitive information by using the (a) back button or (b) history list of the victim's browser, as demonstrated by reading the response page of an https POST request.
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.