trusted_host_patterns

https://www.drupal.org/forum/support/post-installation/2016-06-30/how-to-configure-trusted-host-patterns

https://www.drupal.org/docs/8/modules/skilling/installation/trusted-hosts-setting

$settings['trusted_host_patterns'] = array(
   '^domain\.com$',
   '^www\.domain\.com$',
);