Microsoft 365 Token-Replay Attacks Compromise 97 Accounts at 79 Organizations

Cybersecurity researchers have disclosed a Microsoft 365 campaign that has been observed leveraging an adversary-in-the-middle (AitM) relay to capture sign-in sessions and then replay the stolen tokens to break into email accounts at 79 organizations.

Huntress, which observed the activity between July 14 and September 22, 2026, said it detected 497 successful Microsoft 365 sign-in events across