Substack data breach (2025): was your email exposed?
Substack (substack.com) suffered a data breach in October 2025 that exposed around 663,121 accounts. The leaked records included email addresses and phone numbers. Check whether your email was caught up in it — and lock down your accounts before the data is misused.
Check if my email was exposed — free →What happened in the Substack breach?
Substack (substack.com) was hit by a data breach dated October 2025, exposing around 663,121 accounts. Incidents like this happen when attackers break into a company’s user database, or when a misconfigured server or third-party partner leaks it — and the stolen records then spread among other criminals.
The exposed records included email addresses and phone numbers. Leaked data doesn’t simply disappear: it gets copied, sold and re-posted across breach forums and dark-web markets for years. That’s why your information from the Substack breach can still be abused long after the original incident — and why checking your exposure and locking down your accounts matters even now.
What data was exposed in the Substack breach?
The Substack breach exposed email addresses and phone numbers. The more of these are tied to you, the more ways an attacker can impersonate you or break into your other accounts.
How the leaked Substack data can be used against you
Because the Substack breach exposed email addresses and phone numbers, your email address becomes a target for convincing phishing, often referencing this very breach to look legitimate; and your phone number fuels scam calls and smishing (fraudulent texts).
How to check if you were affected
The leaked records themselves aren’t published openly, so the way to know is to check your email against known breach and dark-web databases. Our free tool does exactly that in a few seconds — no account needed.
Check my email against known breaches — free →What to do if your Substack account was breached
These steps are prioritized for exactly the kind of data the Substack breach exposed.
Add 2FA — ideally an authenticator app or a passkey rather than SMS — to your email, banking and other important accounts, so a stolen password alone can’t get in.
Leaked numbers feed robocalls and smishing. Never act on an unsolicited call or text, enable your carrier’s spam filter, and remove your number from data-broker sites that resell it.
Scammers reference real breaches to sound credible, so treat any email mentioning Substack with suspicion, and never use a password-reset link you didn’t request — go to the site directly instead.
Leaked data is resold for years, so a one-time clean-up isn’t enough. Ongoing breach and dark-web monitoring tells you the moment your details reappear, so you can act before an account is misused.
The Substack breach, answered
Was my email in the Substack breach?
You can find out in seconds with our free breach and dark-web check — enter your email and it tells you whether it appears in the Substack breach and other known incidents.
When did the Substack breach happen?
The Substack data breach is dated October 2025 and exposed roughly 663,121 accounts. Note that breached data often surfaces and is resold long after the original date.
What data was exposed in the Substack breach?
The exposed records included email addresses and phone numbers. Around 663,121 accounts were affected.
What should I do after the Substack breach?
Change your Substack password and any reused passwords, turn on two-factor authentication, watch for phishing that references Substack, and monitor whether your details resurface on the dark web.
Was your email in the Substack breach?
Check free in about a minute — then we’ll help you remove your exposed data and keep it monitored.
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