Substack Reports Data Breach Affecting User Emails and Phone Numbers
- Securityish
- Threats & Incidents
Quick Summary
Substack has notified users of a data breach where attackers accessed email addresses and phone numbers in October 2025. CEO Chris Best confirmed that while some user data was stolen, credentials and financial information were not compromised. The breach was discovered four months later, and a database containing 697,313 records was leaked on BreachForums, prompting warnings about potential phishing attempts.
The Securityish Brief
Substack, a popular newsletter platform, has informed its users about a data breach that occurred in October 2025. The breach involved unauthorized access to limited user data, specifically email addresses and phone numbers, but did not compromise credentials or financial information. CEO Chris Best disclosed that the breach was identified on February 3, 2026, four months after the initial incident.
While Substack has not disclosed the exact number of affected users, a threat actor leaked a database on BreachForums containing 697,313 records of allegedly stolen data. The attackers reportedly used a noisy scraping method to access this information, which has since been patched by Substack.
Substack has taken steps to address the security flaw that allowed the breach to occur. Best emphasized that there is currently no evidence of misuse of the stolen information, but users are advised to exercise caution regarding suspicious emails or text messages.
Implications for Users
This incident highlights the ongoing risks associated with data breaches, particularly for platforms that handle sensitive user information. Users should remain vigilant for phishing attempts that may exploit the leaked data. The breach also serves as a reminder for organizations to prioritize security measures to protect user data.
Substack’s previous privacy lapse in July 2020, where email addresses were inadvertently exposed, underscores the importance of robust data protection practices. As the platform continues to grow, reaching five million paid subscriptions by March 2025, maintaining user trust through effective security measures is crucial.
Key Takeaways
- Be cautious of any unexpected emails or text messages that may be phishing attempts.
- Regularly update your passwords and consider using unique passwords for different accounts.
- Monitor your accounts for any suspicious activity or unauthorized access.
- Enable two-factor authentication (2FA) on your accounts to add an extra layer of security.
- Stay informed about security updates from platforms you use, including Substack.
Key Terms & Concepts
- BreachForums: In this article, BreachForums refers to a hacking forum where stolen data is often leaked and discussed.
- Phishing: Phishing is a type of cyber attack where attackers attempt to trick individuals into providing sensitive information through deceptive emails or messages.
Read the original article here: https://www.bleepingcomputer.com/news/security/newsletter-platform-substack-notifies-users-of-data-breach/
Your 5-Minute Securityish Brief
A weekly digest of cybersecurity news, phishing alerts, privacy tips, and emerging threats, simplified so anyone can understand what matters and why.
Securityish
Securityish explains cybersecurity, scams, data breaches, and privacy risks in simple language so you know what’s happening and how to protect yourself.
© 2026 Securityish
