Substack Breach May Have Leaked Nearly 700,000 User Details Online
ID: 40f19420-024a-51a5-85bd-739c94f32337
STIX ID: report--40f19420-024a-51a5-85bd-739c94f32337
Feed Name: TechRepublic Security
Threat Score
Substack confirmed an unauthorized access incident that occurred in October 2025 and was discovered on February 3, 2026; exposed data included email addresses, phone numbers, and internal metadata, and a threat actor reportedly posted ~697,313 records to a hacking forum, while Substack says credit card numbers and passwords were not accessed and an investigation is underway.
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