Substack data breach
The Substack breach happened on October 23, 2025 and exposed 663,121 accounts. 2 kinds of data were exposed.
Overview
- Site
- substack.com
- Breach date
- October 23, 2025
- Recorded on
- February 6, 2026
- Accounts exposed
- 663,121
- Exposed data
- Email addresses, Phone numbers
- Risk score
- 24 out of 100
Risk based on the exposed data
This breach scores 24 out of 100. The score is driven mostly by Phone numbers, Email addresses.
The risk score is a guide to how dangerous a breach is, judged by the kinds of data exposed. The number of accounts is not included.
Breaches from the same period
- MyVidster (2025) (2025-10-24, 3,864,364 accounts)
- University of Pennsylvania (2025-10-30, 623,750 accounts)
- Zilvia.net (2025-11-06, 287,863 accounts)
What affected users should do
- Passwords were not exposed, but you may receive fake emails aimed at the exposed email addresses.
- Turn on two-factor authentication for your login.
- Phone numbers were exposed, so watch out for impersonation by text message or phone call.
This site organizes publicly available information about data breaches. Data as of February 16, 2026. Breach dates are as originally listed; when only the month is known, the date is recorded as the 1st.