https://www.cnet.com/news/ios-12-0-1-now-available-aims-to-fix-iphone-xs-charging-and-wi-fi-issues/

Some users of the new iPhone XS and XS Max have also complained that the new phones' front cameras are overly "smoothing" selfies, but that appears to be intended functionality of the updated computational photography features.

Install iOS 12.0.1 by following the instructions here.