CORs policies are breaking websites and some work in other browsers!
I know people who migrated away from Firefox I had them using because a site they need broke and then developed the habit of not using Firefox.
You should consider tracking CORs killed websites and automatically testing that list in chrome and use that to create a whitelist of sites that only firefox is breaking due to security settings. This could allow busy sites to be exempt from newer security policies until chrome also breaks them.
Add a broken website option under HELP and use that report system to built up stats. You could detect CORs errors and bring up an error report button.