2024 Kaiser Permanente — 13.4M members (tracking code leak)
Data compromised
Names, IP addresses, sign-in status, navigation behavior, health search terms
Technical writeup
Kaiser Permanente confirmed the largest healthcare data breach of 2024 in April, affecting 13.4 million current and former members. Tracking technologies on Kaiser's websites and mobile apps inadvertently shared patient data with third-party advertisers including Google, Microsoft, and X. Exposed data included member names, IP addresses, sign-in status, navigation behavior, and health encyclopedia search terms.
Root cause
Inadvertent data sharing via tracking code to third-party advertisers