email from ST 10 min ago:
On Wednesday, August 30 we automatically updated your SmartThings Hub v2 to the latest firmware (version 18.22). We apologize that we were unable to provide advance notification of this update as we strive to alert you to updates before applying them. However, due to a critical concern regarding your Hub’s connectivity, we needed to apply the update without advance notification. Your Hub briefly experienced downtime of less than one minute as it rebooted and applied the update.
This update addresses a bug which caused Hubs to go offline for an extended period of time.