is this a bug?

[flimmbing]

Hello,

I noticed that after a user logs out in roundcube he is redirected to the logged off site. But from here he (or someone else) can use the browsers' "back-button" to relogin without needing any login information or password. He can see the roundcube webapp with the imap folder structure and even the emails. After about 3-5 sec. he is redirected to logged of screen again automatically. But he can do that "trick" over and over again.

Anyway to prevent this from happening? 

[flimmbing]

No suggestions on that bug?