Security First: Managing the TFS 2015 Update 4 Patch (TFS-Update_4a-pc.zip)
Typically, these patches include a tfs2015.4.xpatch.exe . Run this on your Application Tier. TFS-Update_4a-pc.zip
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? Security First: Managing the TFS 2015 Update 4