Mozilla is in hot water following a privacy complaint filed by the European digital rights group NOYB (None Of Your Business). The group alleges that Mozilla has been tracking Firefox users without their consent through a new feature.

This feature, called “Privacy-Preserving Attribution” (PPA), was developed in collaboration with Meta (previously Facebook) and rolled out automatically in Firefox version 128 this past July. According to NOYB, despite its name, PPA actually enables the tracking of user activity across various websites.

NOYB’s complaint highlights a key concern: “While the intention may be to improve user privacy, this technology allows Firefox to monitor behavior rather than leaving it to individual sites.” They argue that Mozilla turned this feature on by default without consulting users, raising significant privacy questions.

The PPA feature allegedly allows Firefox to collect data on users’ interactions with ads, bundling this information for advertisers. Mozilla claims that this system improves privacy by helping advertisers evaluate ad effectiveness without compromising personal data. However, NOYB counters that this tracking mechanism still interferes with users’ rights under the EU’s General Data Protection Regulation (GDPR).

Felix Mikolasch, a data protection lawyer at NOYB, remarked, “Mozilla seems to be adopting the advertising industry’s narrative, treating Firefox as an ad measurement tool. While they may have good intentions, this is unlikely to replace cookies or other tracking methods—it simply adds another layer of tracking.”

In a support document, Mozilla described PPA as a “non-invasive alternative” to traditional cross-site tracking. They assure users that the feature does not share individual browsing data with third parties, including themselves, and that only aggregated information about ad performance is shared with advertisers.

Mozilla emphasizes, “PPA means your browser controls the tracking, not the websites. There are strong privacy safeguards in place, including the option to opt out.” Users can easily disable PPA by going to the Privacy & Security settings in Firefox and unchecking the “Allow websites to perform privacy-preserving ad measurement” option.

A Mozilla spokesperson acknowledged the concerns, stating, “We should have engaged more with external voices as we improve online advertising. We’ll work on that moving forward.” They clarified that while the initial code for PPA was included in Firefox 128, it has not yet been activated for broader use, and no user data has been recorded or transmitted.

The spokesperson concluded, “We believe PPA is a vital step toward enhancing internet privacy and look forward to collaborating with NOYB and others to clarify our approach.”

To disable this feature:

  • Open the browser settings.
  • Go to the Privacy & Security page.
  • Deactivate Website Advertising Preferences.