Data breach
Substacksubstack.com
663 121 accounts exposed in a breach dated 2025-10-23.
Breached2025-10-23Added to HIBP2026-02-06 UTCUpdated by HIBP2026-02-06 UTCAccounts663 121Domainsubstack.com
Verified
What happened in Have I Been Pwned’s words
In October 2025, the publishing platform Substack suffered a data breach that was subsequently circulated more widely in February 2026. The breach exposed 663k account holder records containing email addresses along with publicly visible profile information from Substack accounts, such as publication names and bios. A subset of records also included phone numbers.
Exposed data as HIBP classifies it
- Email addresses
- Phone numbers
How HIBP qualifies it
- HIBP verified that the data came from this service.
Source: Have I Been Pwned (CC BY 4.0)
Copied from HIBP 2026-11-05 03:50 UTC