http - AJAX call following 302 redirect sets origin to null

Question

I'm doing an AJAX call from domain A to domain B.

My domain B checks if A is in the list of allowed domains and sets the Access-Control-allow-Origin to domain A. So far, so good.

Domain B responds to the request by sending a 302 redirect to domain C using the Location header.

The AJAX call follows the redirect to domain C but has the header: Origin: null.

I expected the origin header to be set to domain A, after following the redirect.

Can anyone explain to me why the origin is set to null instead of to domain A?

Example

1. Request from domain A to B

   GET / HTTP/1.1
   Host: domain-B.com
   Origin: http://domain-A.com
   

2. Response from domain B :

   Access-Control-Allow-Origin: http://domain-A.com
   Location: http://domain-C.com
   

3. AJAX call follows the redirect to domain C:

   GET  HTTP/ 1.1
   Host: domain-C.com
   Origin: null
   

Answer 1

See here, this seems to suggest its related to a "privacy-sensitive" context.

Are there any browsers that set the origin header to "null" for privacy-sensitive contexts?