Oh, I did not know that. Are you sure that enabling studies also means that user's data is sent to Mozilla without consent? Are you sure about this?

I'm asking because there I can imagine that there is a benefit for Mozilla to develop a feature that enables studies without sending data. It could be used to fix a broken feature or a broken logic (as in the case of expired certificates here). So, I'm not convinced that enabling studies always means that your data gets uploaded without the consent. Can you point me to privacy whitepaper / source code to backup that statement?