If you are using a Mozilla Firefox web browser and that computer is being used by multiple users, then make sure you remember to clear any important private information you have, so that your account will not be reachable by other people that using the same computer. This is because by default, Mozilla Firefox web browser will save your active logins (username and password) for any websites that require login.

Image taken from Sparrow*

Besides, other information such as browsing & download history, form & search history, cookies, cache, and site preferences will be saved.

In order to clear saved passwords in Mozilla Firefox browser:

1. Click on Tools that located on the top part of Mozilla Firefox web browser.
2. Select Clear Private Data from the drop down menu bar (or Ctrl+Shift+Del).
3. A box with few options to clear your visited data will be appearing there.
4. From there you will see Time range to clear, choose Everything from the drop down menu. Tick on the information you want to clear and choose Clear Now.

Alternatively, you can choose to use Start Private Browsing (or Ctrl+Shift+P) to browse privately.