There is also network.http.referer.spoofSource

• https://dxr.mozilla.org/mozilla-release/source/netwerk/protocol/http/HttpBaseChannel.cpp#1260

// false: use real referrer
// true: spoof with URI of the current request
bool userSpoofReferrerSource = gHttpHandler->SpoofReferrerSource();

The Big Fat Fox said

But as completely disabling it (as I know one can do in the about:config settings) breaks some websites. I would like to know if one can configure it so that it is only disabled for when you are going to a website which is a third-party one?

There is a newer preference you could experiment with:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste referer and pause while the list is filtered

(3) Double-click the network.http.referer.XOriginPolicy preference and enter the desired value:

0 => no restrictions (default) 1 => base domain must match (send from a.example.com to b.example.com) 2 => full host name must match (only b.example.com to b.example.com)

So with the default setting, the referrer should be listed on the following page, but with 1 or 2 it should not:

https://www.jeffersonscher.com/res/jstest.php

I have looked and the default value appears to actually be `0`... So should I just minus `1` from each of the values to get what I need and you listed or...?

Oops, yes, somehow I got everything off by one. I'll fix my post.