Substack Data Breach
What Happened
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.
Compromised Data
Recommended Actions
Use a password manager to generate and store strong, unique passwords for all your accounts. 1Password helps protect your data with industry-leading security.
Try 1Password
Get Aura for identity theft and credit protection. Keep your assets safe with fast fraud alerts, instant credit lock, and $1,000,000 identity theft insurance. Speak to a U.S. based fraud specialist 24/7.
Try Aura
Get Guardio for real-time protection after a breach. Guardio blocks AI-generated scam sites, fake login pages, and malicious pages designed to exploit leaked information. Built by cybersecurity specialists who track new threats 24/7, Guardio gives you immediate, expert-level protection plus clear steps to help you secure your accounts instantly.
Try GuardioBreach Overview
-
Affected Accounts:
663.1 thousand
-
Breach Occurred:
October 2025
-
Added to HIBP:
6 Feb 2026
Recommended Actions
Change Your Password
If you haven’t already changed the password affected by this breach, do so immediately on every account where it was used.
Enable Two-Factor Authentication
Wherever 2FA is supported, add an extra layer of security to your account.
Get Guardio for real-time protection after a breach. Guardio blocks AI-generated scam sites, fake login pages, and malicious pages designed to exploit leaked information. Built by cybersecurity specialists who track new threats 24/7, Guardio gives you immediate, expert-level protection plus clear steps to help you secure your accounts instantly.
Try Guardio
Use a password manager to generate and store strong, unique passwords for all your accounts. 1Password helps protect your data with industry-leading security.
Try 1Password
Get Aura for identity theft and credit protection. Keep your assets safe with fast fraud alerts, instant credit lock, and $1,000,000 identity theft insurance. Speak to a U.S. based fraud specialist 24/7.
Try Aura