It was their terms of service change at the start of 2025. It caused quite a shitstorm.

So essentially a bunch of noise that didnt really mean anything concrete?

Mozilla backed down due to the backlash. It still means Mozilla is untrustworthy.

This implies they had some sinister plan to claim all your data as theirs or something which is ridiculous - they didn’t back down from anything but changed the wording of the legal text to make it easier to parse for non-lawyers.

There is no other interpretation of changing "we respect your privacy and do not sell your data" to "we respect your privacy".

Mozilla even tried to claim the old wording was bad because some governments erroneously define "sell" as "to exchange something for valuable consideration, such as money".