Update: Sources say a newer cumulative update has been compiled; build 10586.312 that will likely head to the public instead. Original article follows, just replace all 10586.306 references with .312.
As Microsoft continues work on the upcoming Windows 10 Anniversary Update, a smaller team within the company is focused on providing bug fixes and updates to the latest current branch build of Windows 10, which is build 10586. Right now, Microsoft is testing another new cumulative update that may roll out to the public very soon; build 10586.306.
