Some users may be unable to view location and subject details for other users' Exchange Online calendar items

A post-incident report has been published.

A post-incident report has been published.

Title: Some users may be unable to view location and subject details for other users' Exchange Online calendar items User impact: Users may have been unable to view location and subject details for other users' Exchange Online calendar items. More info: Affected users may have only been able to view the free/busy availability of other users' Exchange Online calendars despite having been configured to also view location and subject details for calendar items. Final status: We've confirmed that the deployment of the solution developed to correct the impacting permissions issue has completed, and we've validated with a subset of affected users that the impact has been resolved by our actions. Scope of impact: Some users who attempted to view Exchange Online calendar items for users' calendars for which they were configured to have access may have been impacted. Start time: Tuesday, July 14, 2026, at 12:00 AM UTC End time: Monday, July 27, 2026, at 8:00 PM UTC Root cause: A recent Exchange Online service change introduced an issue affecting the preservation of calendar-sharing permissions during mailbox moves. The change was implemented to improve folder-copy consistency within the mailbox move process and modified the method used to validate the presence of calendar-sharing permissions. Due to this change, the validation process incorrectly identified these permissions as absent, even when they were configured correctly. As a result, mailboxes moved while the change was active were recreated without their existing calendar-sharing permission settings and instead reverted to the default availability-only configuration. Users who previously had permissions to view additional calendar details, such as meeting subjects and locations, were subsequently limited to viewing free/busy information only, resulting in the impact. Next steps: - For a more comprehensive list of next steps and actions, please refer to the Post Incident Report document. This is the final update for the event.

Title: Some users may be unable to view location and subject details for other users' Exchange Online calendar items User impact: Users may be unable to view location and subject details for other users' Exchange Online calendar items. More info: Affected users may only be able to view the free/busy availability of other users' Exchange Online calendars despite having been configured to also view location and subject details for calendar items. Current status: Our fix is deployed 35 percent to completion and we’re continuing to monitor its progress to provide as estimation of impact remediation by our next scheduled update. Scope of impact: Some users attempting to view Exchange Online calendar items for users' calendars that they're configured to have access to may be impacted. This information may be updated as our investigation continues. Start time: Tuesday, July 14, 2026, at 12:00 AM UTC Root cause: A recent Exchange Online service change introduced a permissions issue that's preventing some users from viewing location and subject details for other users' calendars, which is resulting in impact. Next update by: Monday, July 27, 2026, at 10:00 PM UTC

Title: Some users may be unable to view location and subject details for other users' Exchange Online calendar items User impact: Users may be unable to view location and subject details for other users' Exchange Online calendar items. More info: Affected users may only be able to view the free/busy availability of other users' Exchange Online calendars despite having been configured to also view location and subject details for calendar items. Current status: We’ve completed the aforementioned final validation of our developed code fix and have begun deploying it to the affected environments. We’ll provide a timeline to remediation as it becomes available. When the fix has completed deployment, admins will need to reapply access permissions for the previously impacted users to restore access and fully resolve the impact. Scope of impact: Some users attempting to view Exchange Online calendar items for users' calendars that they're configured to have access to may be impacted. This information may be updated as our investigation continues. Start time: Tuesday, July 14, 2026, at 12:00 AM UTC Root cause: A recent Exchange Online service change introduced a permissions issue that's preventing some users from viewing location and subject details for other users' calendars, which is resulting in impact. Next update by: Friday, July 24, 2026, at 11:00 PM UTC

Title: Some users may be unable to view location and subject details for other users' Exchange Online calendar items User impact: Users may be unable to view location and subject details for other users' Exchange Online calendar items. More info: Affected users may only be able to view the free/busy availability of other users' Exchange Online calendars despite having been configured to also view location and subject details for calendar items. Current status: We’ve confirmed that a recent Exchange Online service change introduced a permissions issue that's preventing some users from viewing location and subject details for other users' calendars. We've reverted the offending service change and are conducting final validations for our developed code fix, which we expect will deploy and remediate impact by our next communications update. Scope of impact: Some users attempting to view Exchange Online calendar items for users' calendars that they're configured to have access to may be impacted. This information may be updated as our investigation continues. Start time: Tuesday, July 14, 2026, at 12:00 AM UTC Root cause: A recent Exchange Online service change introduced a permissions issue that's preventing some users from viewing location and subject details for other users' calendars, which is resulting in impact. Next update by: Thursday, July 23, 2026, at 2:00 AM UTC

Title: Some users may be unable to view location and subject details for other users' Exchange Online calendar items User impact: Users may be unable to view location and subject details for other users' Exchange Online calendar items. More info: Affected users may only be able to view the free/busy availability of other users' Exchange Online calendars despite having been configured to also view location and subject details for calendar items. Current status: We’re continuing the process of developing and validating a code fix to address what we suspect is a permissions issue introduced by a recent service change that’s preventing some users from viewing location and subject details for other users’ Exchange Online calendar to confirm our findings and potentially remediate the impact. Scope of impact: Some users attempting to view Exchange Online calendar items for users' calendars that they're configured to have access to may be impacted. This information may be updated as our investigation continues. Next update by: Wednesday, July 22, 2026, at 9:00 PM UTC

Title: Some users may be unable to view location and subject details for other users' Exchange Online calendar items User impact: Users may be unable to view location and subject details for other users' Exchange Online calendar items. More info: Affected users may only be able to view the free/busy availability of other users' Exchange Online calendars despite having been configured to also view location and subject details for calendar items. Current status: We've edited the Title, User impact, More info, and Scope of impact sections of this communication to align with our current understanding of the affected scenario. After further investigation, we identified that the affected users' mailboxes were recently migrated to alternate portions of storage infrastructure by our service as an automatic load balancing effort. When the migration took place, the permissions that allow users to view location and subject details for other users' calendars weren't properly copied over. We believe this is caused by the aforementioned service change and are developing a code fix designed to correct this issue. Scope of impact: Some users attempting to view Exchange Online calendar items for users' calendars that they're configured to have access to may be impacted. This information may be updated as our investigation continues. Next update by: Wednesday, July 22, 2026, at 1:30 AM UTC

Title: Some users may be unable to view location and subject details for other users' Exchange Online calendar items User impact: Users may be unable to view location and subject details for other users' Exchange Online calendar items. More info: Affected users may only be able to view the free/busy availability of other users' Exchange Online calendars despite having been configured to also view location and subject details for calendar items. Current status: We've identified that some access permissions may not have been moved over during recent mailbox migrations and our findings suggest that a recent service change to how the service checks whether a folder has explicit Free/Busy permissions may be causing this issue. We're reversing the recent service change to confirm whether this is the case and to remediate the impact. Scope of impact: Some users attempting to view Exchange Online calendar items for users' calendars that they're configured to have access to may be impacted. This information may be updated as our investigation continues. Next update by: Tuesday, July 21, 2026, at 6:30 PM UTC

Title: Some users may be unable to view location and subject details for other users' Exchange Online calendar items User impact: Users may be unable to view location and subject details for other users' Exchange Online calendar items. More info: Affected users may only be able to view the free/busy availability of other users' Exchange Online calendars despite having been configured to also view location and subject details for calendar items. Current status: We're continuing our review of details provided by a subset of affected users to help us understand the root cause of impact and a mitigation plan. Scope of impact: Some users attempting to view Exchange Online calendar items for users' calendars that they're configured to have access to may be impacted. This information may be updated as our investigation continues. Next update by: Tuesday, July 21, 2026, at 4:30 PM UTC

Title: Some users may experience reduced calendar visibility as access permissions reset in Exchange Online User impact: Users may experience reduced calendar visibility as access permissions reset in Exchange Online. More info: Affected users may only be able to view the free/busy availability of other users' Exchange Online calendars despite having been configured to also view location and subject details for calendar items. Current status: We're reviewing details provided by a subset of affected users to determine our next troubleshooting steps. Scope of impact: Some users attempting to view Exchange Online calendar items for users' calendars that they're configured to have access to may be impacted. This information may be updated as our investigation continues. Next update by: Tuesday, July 21, 2026, at 12:30 PM UTC