Redirects to external URLs are not allowed by default, use \Drupal\Core\Routing\TrustedRedirectResponse for it.

Domains should be set in the Trusted Host settings of settings.php.

DomainSubscriber.php uses TrustedRedirectRespose.

      if (isset($redirect_status)) {
        // Pass a redirect if necessary.
        $response = new TrustedRedirectResponse($domain_url, $redirect_status);
        $event->setResponse($response);
      }

See domain/README.md for instructions.

I don't think this is a bug. If you have both domains listed in your settings.php Trusted Host Settings, it should work as designed.

I am getting the same error but within the same domain.

This began when I moved the site from a Subdomain on the same account into production and added a redirect in .htaccess from /public_html/ to /public_html/site

Now the browser switches (seemingly) randomly between 'https://mywebsite/node_name' and 'https://mywebsite/site/node_name' and produces the error(s) with respect to authentication pages.

I will provide more specific details if someone will reply demonstrating an interest in helping solve the issue..

As so far it has not been responded to with my requests elsewhere!

@bsa123 Yes I'm having the same issue,
the public pages seem to load OK from the main domain (how that I've redirected to public_html/web in my public_html directory's .htaccess)
but if I add /user to the main domain in order to login in to Drupal, then I get this error.
I can login OK if I use the old/full path: domainname.com/web/user

But I'd love to know how to fix it so I don't have to?

#46 from this thread solved it for me:
https://www.drupal.org/project/drupal/issues/2612160#comment-12953709

BUT...

Now that I have this working,
I've noticed that my "git push..." no longer works.
It may be a coincidence, or it may be due to this redirect in place?

This is the git command I run:
git push origin2live master
note: this has worked on all other occasions for months,

I received an error.
At first I thought I may have had changes on server, so I tried to override them:
git push -f origin2live master

the error that I'm getting when trying to git push to my live shared hosting server is:

Counting objects: 13, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (13/13), done.
Writing objects: 100% (13/13), 1.21 KiB | 1.21 MiB/s, done.
Total 13 (delta 10), reused 0 (delta 0)
To path/to/my/repo/public_html/.git
! [remote rejected] master -> master (Working directory has unstaged changes)
error: failed to push some refs to 'ssh://path/to/my/repo/public_html/.git'

Has anyone else had experiences with this that relate to the changes as per #46?

@auxiliaryjoel, thanks for giving that reference. I was also facing this issue and that solutions worked for me. Now I want to share what steps I did exactly.

1) Made host entry in /etc/hosts
2) Map directory upto the "....../web" in /etc/apache2/000-default.conf
3) Added below snippet in settings.php
```
if (isset($GLOBALS['request']) and
'/web/index.php' === $GLOBALS['request']->server->get('SCRIPT_NAME')) {
$GLOBALS['request']->server->set('SCRIPT_NAME', '/index.php');
}
```
4) Uncomment lines 119 and 123 in /web/.htaccess

And its working perfectly.

#drupalIndiaAssociation

Thank you @shobhit_juyal
This is work for me.
I didn't have to uncomment the lines 119 and 123 in /web/.htaccess