As of 10/17 (Wed), Version 15.3.1 has become available for iOS users.
This is a minor update containing small adjustments and bug fixes.
For more information on the Version 15.3 update, see here.
This update is optional as of 10/17 (Wed), but will become mandatory on 10/18 (Thu) 8:00 PM (UTC-8). You may install this update using your device’s normal procedure (through the App Store).