Substack
What was exposed
Email addressesPhone numbers
What to do if you were affected
- Expect more phishing and spam at this address. Treat messages that reference this company with extra caution.
- Watch for text-message phishing and SIM-swap attempts on your phone number.
Details
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.
Frequently asked questions
What is the Substack data breach?
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...
When did the data breach happen?
This data breach occurred around October 2025.
How many accounts were affected?
Around 663,121 accounts were affected.
What information was exposed?
Exposed data included Email addresses and Phone numbers.
What should I do if I was affected?
Expect more phishing and spam at this address. Treat messages that reference this company with extra caution. Watch for text-message phishing and SIM-swap attempts on your phone number.
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