How do i get to this update - Security update for mDNSResponder
Where do I find the security update for OSX ElCapitan 10.11.6 about the security issue with mDNSResponder?
Question marked as
From the screenshot you posted it clearly states that the Security Update for mDNSRespaonder
is for Mac OS X before Mac OS X El Capitan 10.11.1.
As you are running Mac OS X El Capitan 10.11.6 it is probably included or not necessary.
To check for any available updates for your mac open the App Store and go to Updates.