Impact & Downstream Threats
This breach carries moderate risk due to the nature of exposed data fields and the scale of affected records.
- SIM swap attacks where phone numbers are present
- Targeted phishing campaigns using exposed email addresses
Breach Intelligence
Executive Summary
In early February 2026, Substack confirmed a significant data breach affecting approximately , 697,313 user records, . While the incident was officially disclosed on February 6, 2026, the actual breach occurred months earlier, in , October 2025, .,
, The breach was not a traditional server penetration but a , "noisy" scraping attack, targeting Substack’s API. Threat actors exploited a vulnerability in the platform’s infrastructure to harvest a wealth of user metadata before security systems triggered and patched the flaw. Although Substack’s total user base exceeds 35 million, this specific leak was limited to a subset of nearly 700,000 accounts.,
, The Compromised Data,
The leaked dataset is notable for its depth rather than its breadth. While it did , not, include passwords or credit card numbers, it exposed highly specific personal information, including:,
About Substack
Publishing and newsletter platform for writers and creators.
Data Points Exposed
Dark Web Verification
Status: Confirmed
- Dataset containing approximately 664K records identified in breach intelligence sources.
- The data is indexed and searchable across breach notification platforms.
Recommended Actions
⚠️ Do not assume this is low sensitivity.
Non-clients may request a breach impact review.
Frequently Asked Questions
In February 2026, Substack experienced a data breach that exposed approximately 664K records containing personal information.
The exposed data includes fields such as email address, full name, phone number, username.
Approximately 664K records were affected based on current breach intelligence.
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- A public-facing individual
- A high-profile executive
- A customer of Substack
- Or concerned about credential reuse
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