Substack — Cyber Attacks, Breaches & Threat Activity

Related Threat Clusters

• Substack Breach Exposes User Emails and Phone Numbers from October Hack

  Substack has disclosed a security breach that exposed user email addresses and phone numbers due to a hack that occurred in October 2025. The breach went undetected for four months, with CEO Chris Best confirming that…

  30 articles · Updated February 5, 2026

Recent Intelligence Reports

• Data leak at Substack: Dataset with nearly 700000 entries online — Heise.De · February 6, 2026
• Substack reveals details of historic security breach that exposed user data — Betanews · February 6, 2026
• Substack data breach leaks users’ email addresses and phone numbers — Csoonline · February 5, 2026
• Hacker claims theft of data from 700,000 Substack users; Company confirms breach — Securityaffairs.Co · February 5, 2026
• Substack says intruder lifted emails, phone numbers in months-old breach — Theregister · February 5, 2026
• Substack says intruder lifted emails, phone numbers in months — Theregister · February 5, 2026
• Substack Alerts Users to Data Breach Exposing Emails and Phone Numbers from Late 2025 Hack — Mlq.Ai · February 5, 2026
• Substack warns customers of data breach following hacker's dark web claims — Therecord.Media · February 5, 2026

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