How to make sure Referer header is getting passed

Hi everyone,

I’m rendering a WYSIWYG editor (TinyMCE) on a page in an HTML element:

It’s getting rendered good, except the editor needs to retrieve a Referer header to function properly:

In the console I can see that the header is not getting passed indeed:

I’ve tried to use a Referer Control extension, to find out what blocks it, but with no success (or I’m using it wrong, not sure)

The question is:
How to make sure the Referer header gets sent to TinyMCE? considering that I render it in an HTML element and can’t directly pass headers there.

Any help would be much appreciated! Thanks.