Scenario
You log in to SharePoint on a computer that is not yours. Now that you are
finished, no matter what you do, the next person that logs in to the computer is
logged in as you. They can sign out, close the browser, clear the internet
history, etc. It still logs in as you.
Fix
Found solution here
- Go to User Accounts in the Control Panel
- Click on Manage your credentials
- Look for the SharePoint credentials in the list and remove them
