Newsletter platform Substack notifies users of data breach

Newsletter platform Substack notifies users of data breach

Newsletter platform Substack is notifying users of a data breach after attackers stole their email addresses and phone numbers in October 2025.

Although the incident occurred four months ago, CEO Chris Best told affected users that Substack only discovered the breach this week. However, while the attackers stole some users’ data, Best added that they didn’t access credentials or financial information.

Read more: bleepingcomputer.com