Accessing a local application with XHR request worked in chrome, but Firefox gave the error that Cross-Origin Request Blocked and in fact didn't even read the stream.

This is not a cors problem per se, but the fact that Firefox gave an exception on the certificate which is self-signed.

What must be done:

• In firefox dev tools, open the network tab and copy the url accessed with Options (the devtool gave no status for it)

• copy the adress in the browser (Firefox) : https://localhost:1234/yoururl

  • A message will prompt stating that your connection is not secure
  • click the Advanced button, then Add Exception...
  • Add an exception to https://localhost:1234 (Firefox copied the whole url, just delete the parts and keep localhost:port)
  • Click Confirm Security Exception