"No shady privacy policies or back doors for advertisers" proclaims the Firefox homepage, but that's no longer true in Firefox 128.
Less than a month after acquiring the AdTech company Anonym, Mozilla has added special software co-authored by Meta and built for the advertising industry directly to the latest release
Looks like they are using a Prio based protocol. If they are using Prio2+, I think this article is likely overblown. EDIT: I mixed up my sources - Mozilla tested Prio for telemetry collection. They are using a system called IPA for ads, and I don’t know whether there are formal guarantees for this system