Substack Data Breach
Gravity Score
LowCalculated based on the types of data exposed (2 categories) and the volume of affected records (663,121).
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.
Exposed data
Affected website
substack.com
What to do now
What can we learn from this breach?
Breaches like this offer valuable lessons for the entire industry. Some security practices that help protect data at scale include: encrypting sensitive personal data at rest with properly managed encryption keys; segmenting and isolating databases so that a single breach doesn't expose all records; conducting regular security audits and penetration testing; implementing real-time intrusion detection and incident response plans. Information security is an ongoing process, and each incident reinforces the importance of investing in data protection.
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