Substack data breach exposed user email addresses and phone numbers for months before CEO Chris Best confirmed the October ...

Publishing platform Substack has disclosed a data breach that leaked nearly 700,000 user records after an unauthorized third-party exploited a security flaw.

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

Substack, the hugely popular online content platform with 50 million active subscribers, has confirmed it has been hacked. Here’s what you need to know.

Substack has confirmed a major data breach that exposed emails and phone numbers for approximately 700,000 users, with the ...

The company has emailed affected users after a dark web source claims the data of almost 700,000 users was compromised.