Microsoft on Friday said a validation error in its source code allowed for Azure Active Directory (Azure AD) tokens to be forged by a malicious actor known as Storm-0558 using a Microsoft account (MSA) consumer signing key to breach two dozen organizations. “Storm-0558 acquired an inactive MSA consumer signing key and used it to forge authentication tokens for Azure AD enterprise and MSA consumer to access OWA and Outlook.com,”

Source: The Hacker News