Enclave found that Authenticator for Android exported com.microsoft.identity.client.AccountChooserActivity to any app and built broker requests entirely from caller-supplied fields (package, UID, client ID, redirect URI, scopes). Its signature check compared the claimed app's redirect URI with that same app's installed signature, so it always passed and never checked who was really calling. In Enclave's tests a malicious app with no permissions got Microsoft Graph tokens for the signed-in work account.

Microsoft rates it Important (CVSS 8.6), says it was not publicly disclosed or exploited when published on Sep 8, and lists Authenticator for Android versions 6.0.0 up to but not including 6.2606.4246 as affected.

What to do: check that managed Android devices run Authenticator 6.2606.4246 or later (enforce a minimum app version in Intune if you can), and treat sideloaded apps on devices with work accounts as a token-theft risk.