Attackers Use Fake OAuth Apps with Tycoon Kit to Breach Microsoft 365 Accounts
Aug 01, 2025
Identity Theft / Email Security
Cybersecurity researchers have detailed a new cluster of activity where threat actors are impersonating enterprises with fake Microsoft OAuth applications to facilitate credential harvesting as part of account takeover attacks. "The fake Microsoft 365 applications impersonate various companies, including RingCentral, SharePoint, Adobe, and Docusign," Proofpoint said in a Thursday report. The ongoing campaign, first detected in early 2025, is designed to use the OAuth applications as a gateway to obtain unauthorized access to users' Microsoft 365 accounts by means of phishing kits like Tycoon and ODx that are capable of conducting multi-factor authentication (MFA) phishing. The enterprise security company said it observed the approach being used in email campaigns with more than 50 impersonated applications. The attacks begin with phishing emails sent from compromised accounts and aim to trick recipients into clicking on URLs under the pretext of sharing requests ...
