User impact: Admins may be unable to access and manage configured GDAP tenants in Microsoft Defender.

More info: Impacted admins may find that previously configured GDAP (Granular Delegated Admin Privilege) tenants are no longer visible or accessible within the tenant switcher in the Microsoft Defender portal. In some cases, admins may also encounter messaging indicating access to “0 out of 1 tenants,” despite having valid GDAP relationships and appropriate administrative permissions.

Current status: We’ve completed our mitigation action for the previously identified impacted users and access has been restored for managing GDAP-connected tenants within Microsoft Defender XDR. We’re deploying our code fix and anticipate it will be fully saturated by Friday, June 5, 2026. During this time, we’ll also continue to identify newly impacted users and manually mitigate them to reduce downtime.

Scope of impact: Some admins attempting to access configured GDAP-connected tenants in Microsoft Defender tenant views may be impacted.

Start time: Thursday, May 28, 2026, at 12:00 AM UTC

Root cause: A recent service update to partner–customer relationship functionality introduced a regression that’s causing some GDAP-connected tenants to incorrectly return empty tenant list, resulting in impact.

Reminder that we’ll also have to go back through previous comms and remove any ATL specific language (scope of impact edits, any mentions of “your representatives”, etc.)

Next update by: Friday, June 05, 2026, at 5:30 PM UTC