If someone else signed out of the account without permission, the account and devices should be treated as potentially accessed by another person.
Take these steps:
- Change the account password
- On a trusted device, go to the Microsoft account security page and change the password to a strong, unique one.
- Do not reuse old passwords.
- Check sign-in and security settings
- Review recent sign-in activity on the Microsoft account security dashboard.
- Remove any devices or sessions that are not recognized.
- Turn on additional protection
- Enable two-step verification (if available) so that a code is required when signing in from new devices.
- Sign out everywhere
- Use the Sign out everywhere option on the Microsoft account security dashboard. Within about 24 hours, this signs the account out of browsers, apps, and most devices.
- Sign back in only on trusted devices
- After securing the account, sign in again only on devices that are known and protected with a PIN or password.
If access to Outlook.com, Hotmail, Edge, or OneDrive was involved, also:
- Outlook.com / Hotmail: Go to Outlook.com, select the account picture in the top corner, and choose Sign out. Then sign back in with the new password.
- Microsoft Edge / Bing: On Bing.com, select the account name in the upper-right corner and choose Sign out, then sign in again.
- OneDrive (iOS): Open OneDrive, tap the profile picture, and tap Sign out to remove the account, then sign in again.
If there is any concern that someone is still accessing the account or device, continue working with a trusted adult to review all devices and consider additional help from Microsoft account support.
References: