Response from Microsoft

User impact: Users couldn't freely edit unlocked cells in protected Excel files opened in Excel for the web.

More info: Some users modifying unlocked cells in protected Excel for the web files would receive a prompt that the cells were protected. Affected users could have bypassed the problem by opening files in the Excel desktop app, if accessible.

Final status: We've disabled the offending changes and confirmed through an additional period of monitoring that the issue is resolved throughout the affected environment. Users encountering persistent impact may need to refresh their Excel for the web session to see remediation.

Scope of impact: Some users are impacted when attempting to edit unlocked cells in protected files through Excel for the web.

Root cause: Two recent changes to introduce a new feature that was intended to improve the content latency in Excel for the web resulted in impact.

Next steps:

• We're reviewing our update testing and validation methods to better identify the potential for issues such as this prior to deployment to prevent similar impact in the future.