Midnight Blizzard vs Microsoft: Legacy Tenant to Executive Email
A defunct test tenant, a legacy password without MFA, and a residential-proxy password spray gave Russia's Midnight Blizzard a foothold inside Microsoft's own corporate estate in January 2024 — culminating in stolen executive email and a downstream supplier breach wave. This account explains the password-spray tradecraft, how the actors abused OAuth apps to mine mailboxes, why the failure drew a czar-memo mea culpa, and the SEC disclosure mechanics that made the saga public.