Microsoft warns that with the shift to remote working, customers are exposed to additional security threats such as consent phishing, besides conventional credential theft and email phishing attacks.
Consent phishing is a variant of application-based attack where the targets are tricked into providing malicious Office 365 OAuth applications (web apps registered by the attackers with an OAuth 2.0 provider) access to their Office 365 accounts.
What Is OAuth?
To begin at a high level, OAuth is not an API or a service: it’s an open standard for authorization and anyone can implement it.
More specifically, OAuth is a standard that apps can use to provide client applications with “secure delegated access”. OAuth works over HTTPS and authorizes devices, APIs, servers, and applications with access tokens rather than credentials.
Source: Bleeping Computers