Substack Breach: 662,752 User Records Leaked on Cybercrime Forum

A dataset of approximately 662,752 Substack user records was reportedly posted to BreachForums; analysis shows exposed emails, phone numbers, account creation/update timestamps, internal backend flags, publisher metadata (including monetized creators), profile images, and Stripe customer IDs, suggesting access to internal systems dating back to October 2025. Substack confirmed unauthorized access (no passwords or payment card details reportedly exposed), has remediated the issue, and warns users to watch for targeted phishing and impersonation while the dataset circulates on cybercrime forums.