As you may know, it’s possible for your users to sign-in to SaaS based applications using their Azure AD account. By doing this, a Single Sign On (SSO) experience is created for the user. Before this SSO for an SaaS based application is possible though, the user needs to accept (a) permission request(s) from the application allowing the application to access the users data on its users behalf, even when the user is not using the application.

Added February 11th: Erik Loef pointed me to the following two interesting articles detailing on how oAuth can be used to exploit Office 365 environments. See:

Shining a Light on OAuth Abuse with PwnAuth
Introducing the Office 365 Attack Toolkit

Added May 20, 2020: Microsoft made some new functionality available, please also read my article: “Some welcome additions to the Admin consent workflow in Azure AD” afterwards for the changes Microsoft made.

TL;DR; – Disable user app consent, and enable admin consent requests as soon as possible!

Note: This post reflects the status of Admin consent as of February 9th 2020. Functionality may change, even right after this post has been published.

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