Substack says hackers accessed user emails, phone numbers, and internal metadata in October 2025, with a database of 697,313 records later posted online.

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

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

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

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

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 ...