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Substack Data Breach: Emails & Phones Stolen
6 Feb
Summary
- Unauthorized party accessed limited user email addresses and phone numbers.
- Stolen data reportedly appeared on hacker forums, affecting 697,000 records.
- Users urged to watch for suspicious communications following the breach.

A significant data breach impacted Substack users in October 2025, with the incident coming to light on February 3rd, 2026. An unauthorized party gained access to a limited subset of user data, specifically email addresses and phone numbers. No sensitive information such as passwords or payment details was compromised.
The company has since rectified the security flaw and is conducting a thorough investigation into the matter. Despite no immediate signs of data misuse, a dataset allegedly containing around 697,000 records from Substack was published on the hacker forum Breachforums.
Substack is urging its users to exercise caution and remain vigilant against any suspicious emails or text messages. The full extent of affected accounts has not been officially confirmed by the company.