Since the whole point of cookies is to let the user('s browser) store and return them, you can't trust on them being hidden them at all, ever. In fact, you can NOT trust cookies at all.

And yes, without an expiry date, they should expire on closing the browser.

see the specs

"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re: Hiding cookies from users by Joost
in thread Hiding cookies from users by Anonymous Monk

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