S

Confirmed breach

Substack data breach

Country being checked · substack.com

A breach of Substack was added to Have I Been Pwned’s breach database on 6 February 2026. It affected 663,121 accounts. Exposed: Email addresses and Phone numbers. The breach began on 23 October 2025, 106 days before it was reported.

Status

Confirmed breach

People affected

663,121 accounts

Reported

6 February 2026

Breach began

23 October 2025

Time to tell

106 days (the median in California’s notices over the last year: 154 days)

What was exposed

• Email addresses
• Phone numbers

Sources

• Breach database · 6 February 2026 · 663,121 accountsHave I Been Pwned

Breach databases are read by code. · Corrections and changes

If Substack had your data

1. Look for Substack’s own notice or letter: it should say what of yours was involved. Keep it.
2. Expect scams that use your details: calls, texts or emails pretending to be Substack, your bank or the police. Never give codes or passwords, never approve a sign-in you did not start, never move money.

• Spot the scams that use leaked data →
• What to do after a data breach →

Email me if Substack has another breach

Alert me

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From the data breach tracker: official notices, breach databases and the news, every fact with its source. Open data (CC BY 4.0) · How the tracker works · Official registers · Corrections and changes · Found a mistake? Tell us and we correct it.