Unknown Mozilla dev addon "Looking Glass 1.0.3" on browser

Many people seem to be shocked because Mozilla installed an add-on automatically. In my opinion, it doesn't really matter since the code is coming from Mozilla - they're building the whole browser, so they could introduce functionality anywhere. If someone distrusts their add-ons, why trust their browser at all?

The main question is what behavior is being introduced. I haven't researched deeply, but apparently the add-on does nothing until the user opts-in on studies.

The major problem is that they installed an add-on without properly communicating what it was. A somewhat smaller problem but still a big problem is that was an utterly frivolous add-on that shouldn't have been pushed to people who didn't explicitly want it. But the biggest problem is that Mozilla seems to have trouble understanding why any of those two would be a problem, I want my browser vendor to be serious and not play silly games that can so easily backfire.

Yeah, add-ons from Mozilla merits the same trust as the browser. But this cuts both ways, this stuff undermines my and probably more people's trust in the browser.