Despite Stardust's website promise that user data remains private, Mozilla's latest research reveals the period tracker shares sensitive health information with third-party analytics company RudderStack. Main Developments Mozilla's investigation found Stardust transmits users' birthdate, birth control type, reproductive goals, and specific symptoms to RudderStack. This data is tied to a unique identifier rather than a name, though the FTC has long warned such practices do not ensure anonymity or prevent re-identification. Background Stardust's privacy claim appears on its website, but Mozilla's findings contradict that assurance. The FTC has previously cautioned that replacing names with unique identifiers does not make data anonymous. Read also: Sheryl Sandberg Backs AI Vehicle Inspection Startup with $10M Why It Matters Period-tracking apps handle highly sensitive reproductive health data. Sharing such information with analytics firms raises significant privacy and security concerns for users who trust these apps with intimate details. What's Next Users may reconsider using Stardust or demand clearer privacy policies. The FTC's ongoing scrutiny of health data practices could lead to regulatory action against apps that misrepresent privacy protections.