Tor Browser: CORS Missing Allow Origin

Hello,

I have been running Qubes-Whonix and Tor Browser for 2-3 years, (TB for more).

Recently I noticed I am unable to login at some websites that do CORS requests like:

Main website (where login form shows): foo.com
Login website (where the main site sends an XHR for login): login.foo.net

Note the different TLD for the login website!

This same login works fine in regular clearnet Firefox but I am willing to stay anonymous, as my account was registered anonymously before this host separation.

Looking at browser console I see:

Response body is not available to scripts (Reason: CORS Missing Allow Origin)

What is the workaround for this?
Some setting allowing CORS?