Full Disclosure: A Look at a Recently Patched Microsoft…

### Executive Summary: The report documents a Microsoft Graph authentication logging bypass present from roughly June 2023 to March 2024 where changing the oauth2 endpoint to a different tenant ID allowed attackers to enumerate valid UPNs and verify passwords without creating sign-in log entries in the victim tenant; verbose error codes still revealed credential validity. The author provides proof‑of‑concept scripts demonstrating the technique, test evidence showing missing sign-in logs for the alternate-tenant method, and notes Microsoft internally remediated the issue (VULN-107279) and deemed it low severity.