Personal Data Leak Monitor

Substack data breach

663K accounts from Substack (substack.com) were exposed in this breach. Besides email addresses, it included phone numbers.

Breach date
October 23, 2025
Accounts
663,121
Added to the database
February 6, 2026

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What leaked

Email addressesPhone numbers

What to do now

  1. Do not tap links in emails claiming to be that service
  2. Be alert to fake delivery or unpaid-bill texts and calls

Tools that help with this breach

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About this 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 from Substack accounts, such as publication names and bios. A subset of records also included phone numbers.

Source: Have I Been Pwned (CC BY 4.0)

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