Forgive me if this is old, but I searched and it didn't come up.

When you are on an admin page then click the Log out link and click the browsers back button, latest Firefox, you can still view the admin page you were on. You can view the page, but at least you can not do anything as an admin and when you try you get the "Access denied".

You shouldn't be able to hit the back button and view the admin page you were on after logging out.