@Microsoft patched a critical Entra bug, told me it was not a bug, and never told you it existed.
A broken API authorization flaw was used on 15 separate
@azuread Entra services. Any low-privileged authenticated user in your tenant could download all sorts of logs for the entire enterprise, with no role and no admin rights. That telemetry included source IP addresses, geolocation, MFA status, application access patterns, and the Conditional Access policies applied to every sign-in.
Timeline:
April 8: I reported it to MSRC as VULN-181669 with a video proof of concept attached.
April 23: MSRC said they could not reproduce it and asked for a video.
April 24: I confirmed the video was already in the original submission.
April 27: They closed the case as below the bar for immediate servicing, with no CVE and no bounty, claiming the API enforced permissions server side and returned 403.
April 29: I retested, and the endpoint that had returned a full log dump now returned a role-check error that did not exist when I filed.
They closed the finding as not a bug, and then they shipped the fix for it on the side. That is the opposite of coordinated disclosure.
A single export across the sign-in logs exposed user principal names for every account, source IPs with geolocation, MFA status per sign-in, the full application and service principal inventory, and Conditional Access policy results. In the instance of my finding this resulted in roughly 400 MB of tenant-wide authentication data from one service. The same flaw appeared in 14 more, including Provisioning Logs, ID Protection, Conditional Access, Authentication Methods, Billing - Licenses - Audit Logs and Certificate Authorities. This was not a single misconfigured endpoint. It was one broken authorization pattern repeated across the platform.
The bug is gone now, and without notification, that is precisely the problem. You cannot reproduce it, and Microsoft has published no CVE and no advisory confirming it was ever there. Without that disclosure, you have no exposure window to investigate and no indicators of compromise to hunt. The exploit traffic would show up in your logs as 200 responses to auditLogs/signIns from users who never had read access, but nothing from Microsoft tells you where to look.
Microsoft should reopen VULN-181669, notify affected customers, publish indicators of compromise, and issue the CVE.
Full writeup:
lnkd.in/gXSVwXgZ
@InsiderPhD @DoerrfeldBill @chrishonda0716 @ryanrutan @EdwardLichtner @JoseHaroPeralta @nicfill