https://www.theregister.co.uk/2019/04/15/microsoft_users_pwned/

Microsoft says miscreants accessed some of its customers' webmail inboxes and account data after a support rep's administrative account was hijacked.

The Redmond software giant has sent Hotmail, MSN, and Outlook cloud users notifications that the unnamed customer support rep's account was compromised by hackers who would have subsequently gained "limited access" to certain parts of some customer email accounts, including the ability to read messages in particular cases.