A debug flag accidentally left enabled in production builds of multiple Microsoft 365 Android apps disabled a security check that restricts account token sharing to trusted Microsoft applications. As a result, any app installed on the same Android device could silently request and receive the signed-in user’s authentication token, granting full access to email, files, calendar, and the ability to send messages on their behalf. No user interaction, credentials, or elevated permissions were required to exploit this.

Architect’s Take: Audit your mobile application management (MAM) and Conditional Access policies to ensure app-based controls are enforced at the resource level and are not solely reliant on client-side token handling. Until Microsoft confirms a fully patched build is deployed, consider enforcing Continuous Access Evaluation (CAE) and restricting M365 access on Android to Intune-managed devices with compliant app versions.

Original advisory: Microsoft 365 Android Apps Let Any App Steal Account Tokens via Leftover Debug Flag