"Hello Windows Insiders, today we are releasing Windows 10 Insider Preview Build 20279 (FE_RELEASE) to Windows Insiders in the Dev Channel. This build is largely the same as Build 20277, but we wanted to test our ability to quickly follow-up a flight with another flight.
Windows Insiders who updated to Build 21277 (RS_PRERELEASE) last week will not be offered this build as they are on a newer build. We are working on getting a new build out to those Insiders soon. We expect to move all Insiders in the Dev Channel back to receiving builds from RS_PRERELEASE sometime after the holidays."