Dashboard FE does not use any kind of database so all user data (user settings, information and auth tokens) are stored client side. When you log in you use your instance's login form so Dashboard FE has NO WAY of knowing your user and password. If you feel your Dashboard FE session has been compromised, you can always go to your instance's user settings and revoke the access to Dashboard FE.
However, all actions you perform inside the frontend (posting, favs, rts, etc) pass through the frontend, but they are not stored in any way. It is encouraged that you set up your own instance of #DashFE so you are sure that your data remains safe