The European privacy group noyb has filed a formal complaint against Mozilla, accusing the company of enabling a user-tracking feature in its Firefox browser without obtaining consent.

The feature, known as “Privacy Preserving Attribution” (PPA), allows Firefox to store advertising interaction data directly, bypassing individual websites. This approach has drawn parallels to Google’s controversial “Privacy Sandbox.”

While Mozilla argues that PPA is a less invasive alternative to traditional cookie tracking, noyb contends that it still violates user rights under the European Union’s General Data Protection Regulation (GDPR).

noyb claims that Mozilla activated PPA by default in a recent update without notifying users or seeking their consent, which undermines Firefox’s reputation as a privacy-focused browser.

Felix Mikolasch, a noyb lawyer, criticized Mozilla for adopting an industry narrative that normalizes tracking, asserting that PPA adds to existing tracking methods rather than replacing them.

The complaint urges the Austrian Data Protection Authority to investigate Mozilla’s practices and calls for the deletion of any data processed unlawfully.

This change could impact millions of European users, raising concerns about Mozilla’s ability to balance privacy with ad measurement.