Substack
substack.com
About This Breach
Substack, a publishing and newsletter platform, suffered a data breach in October 2025 that was later circulated more widely in February 2026. The breach exposed 665k account holder records containing email addresses along with publicly visible profile information from Substack accounts, such as publication names and bios.
Data Exposed
Breach Details
| Breach Type | Data Breach |
| Searchable | Yes |
| Verified | Yes |
| Sensitive Data | No |
| Reference | No reference available |
Frequently Asked Questions
When did the Substack data breach happen?
Substack was breached in Oct 2025. The breach was added to the XposedOrNot index on February 7, 2026.
How many records were exposed in the Substack breach?
665,183 records were exposed, making it the #461 largest of the 763 breaches in our index.
What data was exposed in the Substack breach?
The exposed data includes: Email addresses, Phone numbers.
What should I do if I was affected by the Substack breach?
Change your password on the affected service (and anywhere you reused it), turn on two-factor authentication, and set up free breach alerts on XposedOrNot so you know the moment your email appears in a new breach.
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What Should You Do?
Enable Two-Factor Authentication
Add 2FA on all supported accounts using an authenticator app like Google Authenticator or Authy.
Watch for Phishing Calls & SMS
Be cautious of unexpected calls or texts asking for personal information.
Monitor Your Accounts
Set up login alerts and review account activity regularly for suspicious access.