A sixth and perhaps final build has landed in the Chrome OS Dev Channel. Build 66.0.3359.48 (Platform version: 10452.22.0) is now available to devices in what is considered the Alpha channel of Chrome OS and you can download it by typing chrome://help in the browser bar. This is the sixth consecutive week that a new build has made its way into the Dev Channel and is somewhat rare. Most of the time only 4 or 5 builds land here before the build is bumped up to the Chrome OS Beta Channel.
As for what is new, the Chromium team has released a partial log in the Git for the build. Review it, most of the changes are security and performance changes since the latest Dev build.