Substack data breach exposed users’ emails and phone numbers

Substack is notifying some users that the email addresses and phone numbers linked to their accounts were exposed in a "security incident" last year. In an email to account holders, Substack CEO Chris Best said that a hacker had accessed internal data without authorization in October 2025, but that passwords, credit card numbers, and other financial information remain secure.

"On February 3rd, we identified evidence of a problem with our systems that allowed an unauthorized third party to access limited user data without permission...