It's not a Linux issue , but you can give one advice to your friends.
Users of outlook.com or hotmail.com, Microsoft’s two email services, should take note now. Information are stored in cookies when you use the site including whether you have successfully authorized your account or not. If the information is available, you can open and close both services without having to log in again to one of them.
Another problem it's:
It needs to be noted that Microsoft is not the only company that is affected by this. Google Drive for example faces a similar issue. When the software is running, you can click on links to open the Google Account on the web without re-authentication.
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