Typically, these patches include a tfs2015.4.xpatch.exe . Run this on your Application Tier.
Security First: Managing the TFS 2015 Update 4 Patch (TFS-Update_4a-pc.zip)
Check your Microsoft.TeamFoundation.Framework.Server.dll version in the Application Tier\Web Services\bin folder to confirm your current patch level.
Addressing bugs in Kanban board card styles and Batch API results. Pre-Installation Checklist
Check the official Microsoft DevOps Blog for the latest patch notes and security advisories. Team Foundation Server 2015 Update 4 Release Notes
Use the command line with the /CheckInstall flag (if available) or verify the file version in your installation directory to ensure the patch was applied correctly. The Path Forward: Time to Upgrade?