[Zope] Security question

As far as authorization goes, I've noticed that I get prompted for a user-name/password only once during a session. After you've been validated, it appears zope does not prompt you again for that browser session. The reason I'm concerned is that if I have to do maintenance on someone else's web browser, how do I ensure that after I leave a person cannot use the back button or history list to gain manager access to the site? Do I have to exit the browser when I'm done?