Chrome Version       : 65.0.3325.181
OS Version: OS X 10.13.3
URLs (if applicable) :
Other browsers tested:
  Add OK or FAIL after other browsers where you have tested this issue:
     Safari:
    Firefox:
    IE/Edge:

What steps will reproduce the problem?
1. Open a web page that does a CORS request via file://
2. Try to make a communication

What is the expected result?
The communication to work given the CORS headers are proper


What happens instead of that?
It does not work.

(It broke an app that has been used for years.)


Please provide any additional information below. Attach a screenshot if
possible.
Chrome, like FF, sends "Origin: null" in the Request header.

My server implementation sends back response with header "access-control-allow-origin: null".

Chrome refuses this response and gives the following error in the console: "'Access-Control-Allow-Origin' header has a value 'null' that is not equal to the supplied origin. Origin 'null' is therefore not allowed access."

I think that means, according to Chrome null is not equal to null.

Per https://html.spec.whatwg.org/multipage/origin.html#concept-origin-opaque: "An opaque origin
An internal value, with no serialization it can be recreated from (it is serialized as "null" per serialization of an origin), for which the only meaningful operation is testing for equality."

I believe this should work.

UserAgentString: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/65.0.3325.181 Safari/537.36