It seems like Microsoft is desperately trying to influence the migration to Windows 10 with the release of KB3123862, but “experts” recommend avoiding this update.
If you want Windows 10 (and have lived under a rock for the past year and didn’t know about the free upgrade), then install this update.
If, for some strange reason,you did NOT want to install Windows 10 (due to lack of backwards compatibility, included telemetry, software incompatibilities, hardware driver problems, forced albeit sometimes delayed updates that may or may not work properly, start screen advertisements, unscheduled software uninstallations, Cortana, Edge, legacy hardware incompatibilties, etc.), then do not install this update until Microsoft provides more information. This update (although optional) is akin to KB3035583.
Side note:
Yes. I do know about GWX Control Panel and Never10. You do not need to educate me again. Already blocked unintended OS upgrades…