May 17, 2016
As usual, the principal OS X update applies to the current flavour of the operating system, El Capitan (OS 10.11), with a separate security update to patch the two versions before that, Mavericks (10.9.5) and Yosemite (10.10.5).
Users of OS X 10.8 and earlier are out of luck: those versions are in the same boat as Windows XP when it comes to security – unsupported and unpatched.
The Safari patch arrives along with the El Capitan 10.11.5 download; on earlier versions of OS X you’ll need to update it separately.