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Excel.SensitivityLabelAbacAttribute removed in Office.js beta (preview API)

Preview · ExcelApi BETAMicrosoft's documentation

Excel.SensitivityLabelAbacAttribute, a preview API (ExcelApi BETA), removed on the Office.js beta CDN in 16.0.20606.15070, first seen 14 Oct 2026, 20:07 UTC. Affects Excel on Android, iOS, Mac, web and Windows. Not changed in production so far.

Production
No change seen on the production CDN.
Beta
removed in 16.0.20606.15070, first seen 14 Oct 2026, 20:07 UTC; rollout complete 16 Oct 2026, 04:50 UTC.

What this means for your add-in

On clients that load the new build, Excel.SensitivityLabelAbacAttribute is undefined: calling or constructing it throws a TypeError (the messages are below).

This is a preview API (ExcelApi BETA): Microsoft says not to use it in production, and it can change or disappear in any build. If you use it anyway, check that it exists before every use — if (Excel.SensitivityLabelAbacAttribute) { … }. A requirement-set check does not help: preview APIs belong to no released set.

So far this is only on the beta CDN (/lib/beta/hosted/). Add-ins that load production Office.js (/lib/1/hosted/) are not affected yet; production builds often follow beta.

Errors you may see

In the add-in's console or error logs, on clients that loaded the new build. Parts in <…> come from your own code.

  • TypeError: Excel.SensitivityLabelAbacAttribute is not a constructorWindows, web, Android (Chromium)
  • TypeError: Excel.SensitivityLabelAbacAttribute is not a functionWindows, web, Android (Chromium)
  • TypeError: Right-hand side of 'instanceof' is not callableWindows, web, Android (Chromium)
  • TypeError: Cannot read properties of undefined (reading '<member>')Windows, web, Android (Chromium)
  • TypeError: undefined is not a constructor (evaluating 'new Excel.SensitivityLabelAbacAttribute(…)')Mac, iOS (Safari)
  • TypeError: undefined is not an object (evaluating 'Excel.SensitivityLabelAbacAttribute.<member>')Mac, iOS (Safari)

Change history

Change
Build
Severity
Hosts
removed
function preview API
16.0.20606.15070
beta 14 Oct 2026, 20:07 UTC
Complete
low
Excel on AndroidExcel on iOSExcel on MacExcel on webExcel on Windows

Changed in the same rollouts

Source

silentship samples every Office.js file on the CDN every 10 minutes and compares the public API surface of each new build with the previous one by reflection. This page lists what changed for Excel.SensitivityLabelAbacAttribute; it does not include Microsoft's code. The API status comes from Microsoft's published type definitions (@types/office-js and @types/office-js-preview). Documentation: Excel.SensitivityLabelAbacAttribute on Microsoft Learn.