Substack, the hugely popular online content platform with 50 million active subscribers, has confirmed it has been hacked.

The hacker claims to have stolen nearly 700,000 Substack user records, including email addresses and phone numbers.

Substack said that customer data was accessed in October 2025, but wasn't discovered until early February.

Lynch Carpenter is a national class action law firm with offices in Pennsylvania, California, and Illinois. Our firm has represented millions of clients in data privacy matters for more than a decade ...

The digital publishing platform Substack has told some of its users that their data was stolen in a security breach. The ...

Substack states that the security flaw has now been fixed and that a full investigation is underway. There are currently no ...

Newsletter platform Substack has confirmed it suffered a security incident, leading to the compromise of users’ email addresses and phone numbers. Chris Best, the CEO of Substack, notified users of ...

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