Unknown Mozilla dev addon "Looking Glass 1.0.3" on browser

Anyone know how I can turn off Firefox sending technical details and interactions?

Everytime I turn this off, and restart FF it's on again.

58.0b11

If you are on a Nightly or Developer build, you can not turn it off, I asked on Mozilla’s IRC.

Downloading these builds is considered opt-in into telemetry, and toolkit.telemetry.enabled is hardcoded to enabled, the opt-out checkbox literally does nothing, I was told. And about:config confirmed this.