A couple days ago, i wrote a blog post about how firefox don’t delete cookies from Pin Tabs here.
A friend of mine D. Glynos from census suggested to me that this problem/feature may be related to session cookies.
I was troubled about it and today i did a little research on the matter.
So when using firefox session restoration feature, firefox keeps all the session cookies in place and you can continue your work without a problem. If you hit F5 (refresh page) then the session is terminated and you have to log-in from the start.
OK, i don’t use session restoration but Pin Tabs. Seems that firefox considers Pin Tab as a session restoration process and that’s why it keeps the session cookies.
And this is by design !!!!!!!
There is also a 7 years bug (still opened - click here) that applies on Pin Tabs also.
Till now, i have not found a config (in about:config) option to tell firefox NOT to keep the session cookies when closing the browser!