Substack Vulnerability Disclosure Policy

We take the security of our systems seriously, and we value the security community. The disclosure of vulnerabilities helps us ensure the security and privacy of our users.

Guidelines

We require that all researchers:

Make every effort to avoid privacy violations, degradation of user experience, disruption to production systems, and destruction of data during security testing.
Perform research only within the scope set out below.
Use the identified communication channels to report vulnerability information to us.
Keep information about any vulnerabilities you’ve discovered confidential between yourself and Substack until we’ve had 90 days to resolve the issue.

If you follow these guidelines when reporting an issue to us, we commit to:

Recognize your contribution on our Security Researcher Hall of Fame, if you are the first to report the issue and we make a code or configuration change based on the issue. Note that we don’t offer any monetary compensation at this time.
Work with you to understand and resolve the issue quickly (including an initial confirmation of your report within 72 hours of submission).
Not pursue or support any legal action related to your research.

In Scope

substack.com
reader.substack.com
Substack's iOS app

Out of Scope

Any services hosted by 3rd party providers and services are excluded from scope. Any web apps or surface areas meant for employees of Substack are also excluded from scope.

In the interest of the safety of our users, staff, the Internet at large and you as a security researcher, the following test types are excluded from scope:

Findings from physical testing such as office access (e.g. open doors, tailgating)
Findings derived primarily from social engineering (e.g. phishing, vishing)
Findings from applications or systems not listed in the ‘Scope’ section
UI and UX bugs and spelling mistakes
Network level Denial of Service (DoS/DDoS) vulnerabilities

Things We Do Not Want to Receive:

Personally identifiable information (PII)
Credit card holder data

Reporting a Security Vulnerability

If you believe you’ve found a security vulnerability in one of our products or platforms please send it to us by emailing security@substackinc.com. Please include the following details with your report:

Description of the location and potential impact of the vulnerability.
A detailed description of the steps required to reproduce the vulnerability (POC scripts, screenshots, and compressed screen captures are all helpful).
Your name/handle and a link for recognition in our Hall of Fame.

If you’d like to encrypt the information, please use our PGP key.

KeyID: 4ED9E010

Key Type: RSA

Key Size: 4096/4096

UserID: Substack Security security@substackinc.com

Fingerprint: 0A22 F8A8 0456 2638 DD74 BA94 2D86 525E 4ED9 E010