Apple has just released the first beta versions of OS X Yosemite 10.10.5 It's from iOS 8.4.1.
The first beta of OS X 10.10.5 (build 14F6a) is available through both the Apple website and the Mac update system (built into the Mac App Store; only for those who are able to receive betas from OS X) and do not have no specific focus area at least in this build.
Although Apple has not reported anything about the update, the first beta of iOS 8.4.1 (build 12H304) most likely brings general corrections (some, perhaps, related to Apple Music, released on iOS 8.4).
Both versions are only available to developers. It is worth noting, however, that anyone can already test public beta versions of OS X El Capitan 10.11 and iOS 9. To do this, I need to register with the Apple Beta Software Program and understand the risks of using software that is still in the development phase. development.