Disable navigator.send_beacon().
The call: https://developer.mozilla.org/en-US/docs/Web/API/Navigator/sendBeacon
The pref: beacon.enabled
While this is briefly touched upon in #17718 (moved), it deserves separate discussion.
This API runs counter to "Transparency in Navigation Tracking", and the HTML equivalent (<a ping="...">
) is currently disabled (browser.send_pings
is set to false by default even with standard Firefox).