Stardust, a period-tracking app, is sending users' reproductive health data to a third-party analytics company, according to Mozilla research published Wednesday.
Mozilla tested several period-tracking apps and found significant privacy disparities between them. Stardust was flagged for sharing health data with an analytics firm. At least one other app in Mozilla's review fared far better on privacy. Mozilla's published summary does not identify the analytics company or the privacy-respecting rival app by name.
The findings land at a moment when period-tracking apps face unusually high stakes. In states with abortion restrictions enacted after the Supreme Court's 2022 Dobbs decision, reproductive health data is not just personal; it can be legally consequential. Users choosing between apps in the store have almost no way to tell the difference in privacy practices from the listing page alone.
Mozilla has been publishing privacy reviews of consumer apps for years. Companies flagged in those reports rarely move fast to change their data-sharing arrangements. Users, however, sometimes do.