Networking UnityWebRequest - 'x-unity-version' header blocking CORS requests

I'm having trouble using UnityWebRequest that's now no longer considered 'Experimental' in Unity 5.4 to perform certain web requests due to extra headers being included within HTTP messages. This issue is only problematic with WebGL because it is invoking CORS request security problems.

Code (JavaScript):

1. Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at [url]. (Reason: missing token 'x-unity-version' in CORS header 'Access-Control-Allow-Headers' from CORS preflight channel).

I've done a search and have found two threads, both unanswered. I'm sure it has a purpose or it wouldn't be there, but please make it possible for us to switch this header off for scenarios like this.

For reference, these are the two threads I've found:
http://forum.unity3d.com/threads/remove-x-unity-version-from-www-get-post.289704/
http://answers.unity3d.com/questions/1163449/cors-request-blocked-due-to-x-unity-version-header.html

 

@Schubkraft Will these various fixes for 5.4 get backported to 5.3 in patch releases?