A small security update has been released by the Chrome OS team for all devices running the platform. The update is 55.0.2883.105 (Platform version: 8872.76.0) for those keeping score at home. There are not many details in the release notes about the update other than the customary bug and security fixes that come with all updates to the platform. Still, if you are running a Chromebook or Chromebox, get the update so you have the latest and greatest (and safest) version.
All devices will have the update pushed to them over the course of the next few days but if you want to force the issue now, you can do so by going to chrome://help on your Chromebook and tapping the Check for update button. This will download the update and after a reboot you will be running the new build.