Regarding the "Active Directory Leaks via Azure", I think this article is incorrect and misleading at least.
First problem described as "Authenticate to your webmail portal (i.e. https://webmail.domain.com/) and Change your browser URL to: https://azure.microsoft.com/" simply does not result in the acceess the author is describing there (tested), unless maybe if the user is logging in as an Azure Administrator (but maybe not event then, I could not test this). The O365 email url is outlook.office365.com (with some other options available), so webmail.domain.com is not a very good example, again denotes lack of basic knowledge in these MS products. But no doubt that if you are an Azure Administrator with correct permissions you can see all users and more... My assumptionn is that the author used an account that was also Azure Admin and did not realise this.

The following actions also assume that the "attacker" has already stolen Admin credentials/session - like this would be so easy to do!
Of course if you can hijack admin session or steal credentials the options are limitless, no need to read the article to know this.