Mostly login details are saved if you have either saved the passwords or you have cookies saving these details. Deleting the cookies folder and not saving passwords would solve the problem and it's not possible that the details are available on all computers like the cafe where you haven't been logged in earlier. Saving login details on your own computer/phone also is dangerous as if your computer/phone gets hacked, the hacker can directly access your account. In the phone as well I keep deleting data everyday and prefer logging in everytime I access the app.