IT Pro report this morning that Microsoft warns of phishing campaign targeting OAuth tokens.
Hackers have been targeting Microsoft 365 users with a fake app that steals their OAuth authentication token, giving them full access to the victim’s email, calendar, and contacts. Microsoft picked up news of the new cybercrime campaign from Twitter user @ffforward. They discovered that the perpetrator has been targeting Microsoft 365 users with an app called Upgrade, using the publisher name Counseling Services Yuma PC.
The phishing group has been sending emails to potential victims with an OAuth request. OAuth is a form of authentication that uses software tokens to maintain access to an online service such as Microsoft 365. Once the user has signed into a service, it sends an OAuth token to the client device which is then able to access the service without a password for an extended period. When a phishing victim clicks on the OAuth URL in the phishing email, the app will generate an OAuth consent prompt. If the victim then agrees to give the app access, the attackers get the authorization token and can then access the user’s data. The OAuth token allows them to stay in the victim’s account until the token expires or is revoked.