The full installer is actually responsible for installing the browser; it’s what the stub launches in order to do the “real” installing work, but it’s also available separately. It uses a traditional “wizard” interface design, as is (somewhat) natively supported by NSIS. It can also be configured to launch in a silent mode, suitable for scripting or managed deployments.
The installer writes
installation_telemetry.json to the install location, this is read by Firefox in order to send a telemetry event, see the event definition in Events.yaml (category
installation, event name
first_seen) for a description of the properties. There is also an
install_timestamp property, which is saved in the profile to determine whether there has been a new installation; this is not sent as part of the ping.