Telemetry probes in Firefox/Gecko go through a common telemetry core that contains a kill switch. That code is located at https://searchfox.org/mozilla-central/

Telemetry probes in Firefox/Gecko go through a common telemetry core that contains a kill switch. That code is located at https://searchfox.org/mozilla-central/source/toolkit/components/telemetry https://searchfox.org/mozilla-central/source/toolkit/compone.... Have fun.