I don't understand why you've opened another thread about this topic.
Anyway, I'm quoting my reply for your first question:
There is no session:
Existing browsers retain authentication information until the tab or browser is closed or the user clears the history. HTTP does not provide a method for a server to direct clients to discard these cached credentials. This means that there is no effective way for a server to "log out" the user without changing the realm periodically, directing the user to close the browser, or using sessions in the URL.
And I don't think you have to worry about it. Recently, Manuel removed all modifying GETs and introduced CSRF magic tokens to the webgui.