I haven't seen it. I just close the tab if necessary. 
So if some dingaling had access to your computer briefly the could open a browser, enter 1 see what IP's come up, click and wreak havoc?
No logout button?> Cray
You should be able to delete browser history. In some last .... minutes.
But no logout that i know of. Do you have a reason you need to logout?
Most things that you need to log in to would be well served with a way to log out as well. Somebody closes their browser, but they are not logged out. If someone opened a browser and hit 1 they'd have access to all your machines. I guess it is force of habit.
