Found following from the links from the post:

2023-07: Hackers stole a Microsoft Azure Active Directory certificate which gave them full access to basically all Microsoft cloud services including Outlook, Office, SharePoint, Teams, "Login with Microsoft", and so forth. (MS blog entry [1], Source[2], German source)

Also the following:

https://infosec.exchange/@briankrebs/110820474957163710

Quite damning if true.

[1]: https://www.microsoft.com/en-us/security/blog/2023/07/14/ana... [2]: https://www.wiz.io/blog/storm-0558-compromised-microsoft-key...