Apple has just released the first developer beta of OS X El Capitan 10.11.6. Interested developers will find the configuration utility needed to install the release can be found at Apple's Mac Developer Resource Center. It can also be installed from the Updates section of the Mac App Store on a machine running the previous beta.

OS X El Capitan

It's not known at this time what OS X 10.11.6 brings along with it, though it likely contains some bug fixes and performance improvements.