A new cumulative update (October 2026 CU) has been released for Office Online Server.
OOS Build: 16.0.10417.20228
Important before installation:
Updating Office Online Server requires removing the server from its farm and then recreating the farm or joining the updated farm. Follow the instructions in How to update Office Online Server.
Office Online Server CU – KB article describing the CU:
Office Online Server CU – CU download link:
Important notes
Note for this CU:
The original release of Microsoft Office Online Server must already be installed before you apply this security update.
Included fixes and improvements
Office Online Server
KB5002928 addresses vulnerabilities in Microsoft Excel involving remote code execution and information disclosure. Microsoft lists the following security advisories: