Product group released February 2017 Cumulative Update and it is available for download
- KB 3178718 — SharePoint Server 2016 language independent (build number 16.0.4522.1000)
- KB 3178721 — SharePoint Server 2016 language dependent fixes (build number 16.0.4522.1000)
- KB 3127895 — Office Online Server 2016 (language dependent fixes)
Direct link to download updates
- Download April 2017 Update for SharePoint Server 2016 (language independent)
- Download April 2017 SharePoint Server 2016 (language dependent fixes)
- Download April 2017 Office Online Server 2016 (language dependent fixes)
Please run SharePoint Configuration Wizard aka PSConfig on every server on the farm.
You could use this PowerShell script in order to determine your SharePoint farm patch level.
Note: Install cumulative updates into test environment first and just in order to keep your production first. If update deployment was okay, then continue with a production environment. In any case, it will be nice to have backups.