Apple has just released OS X El Capitan 10.11.6 update, available as usual through the App Store, with downloadable standalone Delta and Combo updaters to follow.
The release notes claim that this update improves stability (let’s hope so!), compatibility, and security. Specific improvements mentioned include fixing a bug that could prevent settings being saved in accounts with parental control enabled, and another which prevented network devices such as speakers and multifunction printers from accessing SMB share points. There are also some enterprise fixes concerning NetBoot and Active Directory authentication.
This update includes plenty of security fixes too, which I will summarise later. The total download, including the iTunes update, is around 592 MB.
I will post further details once I have updated here.
Accompanying this is iTunes 12.4.2, iOS 9.3.3, watchOS 2.2.2, and tvOS 9.2.1.