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Security report for substack.com

Substack, Inc. · Technology · United States

Medium risk. 4 critical or high findings in Security headers, GDPR outside view and 1 other check.

Security score

75/100

Risk levelMedium

0–100, higher is better. How it is calculated

Substack, Inc. operates a leading technology platform that empowers independent writers and creators to publish newsletters and monetize their audiences through subscriptions. The platform emphasizes ownership and editorial control, targeting independent voices seeking direct engagement with their readers. The website demonstrates a modern technical infrastructure using React and Preact frameworks, optimized for performance and mobile responsiveness. Security posture is strong with HTTPS enforcement and comprehensive security headers, though privacy compliance documentation is lacking. Overall, the site is professional and trustworthy, but would benefit from explicit privacy and cookie policies and clearer contact information to enhance compliance and user trust.

Scanned

NIS2 and GDPR posture

GDPR outside view
58/ 100 · Medium
Checks completed
7of 7

NIS2 Art. 21(2)

  1. (a) Risk analysis and security policies: Not visible from outside
  2. (b) Incident handling: One indicator
  3. (c) Business continuity, backups and crisis management: Not visible from outside
  4. (d) Supply chain security: Not visible from outside
  5. (e) Secure acquisition, development and maintenance, including vulnerability handling: Partly checked
  6. (f) Assessing the effectiveness of security measures: Not visible from outside
  7. (g) Cyber hygiene and security training: Not visible from outside
  8. (h) Cryptography and encryption: Partly checked
  9. (i) HR security, access control and asset management: One indicator
  10. (j) Multi-factor authentication and secured communications: Not visible from outside

This scan rated NIS2 with an earlier keyword method that is no longer shown; rescan for the per-article view. Risk management, continuity, supply chain, training, MFA, management oversight (Art. 20) and incident reporting (Art. 23) need internal evidence, and Guard cannot tell whether NIS2 applies to this organisation.

GDPR is indicative only, based on publicly visible signals: Articles 7, 12, 13 and 32 of Regulation (EU) 2016/679 and Article 5(3) of the ePrivacy Directive. Not a certification or legal assessment.

Priority findings

4 findings rated critical or high. Fix these first.

  1. Security headers

    Security headers are instructions your web server sends to every visitor’s browser. Missing ones leave visitors more exposed to attacks such as clickjacking and injected scripts.

    • High

      Missing X-Frame-Options header

      Prevents clickjacking attacks

      What to do: Add "X-Frame-Options: DENY" or "X-Frame-Options: SAMEORIGIN"

  2. GDPR outside view

    These are the privacy signals visitors and data protection authorities look for under GDPR.

    • High

      No Cookie Policy found

      GDPR requires clear information about cookie usage

      What to do: Add a dedicated cookie policy explaining cookie usage and purposes

    • High

      No Cookie Consent Banner found

      GDPR requires explicit consent for non-essential cookies

      What to do: Implement a cookie consent banner that appears on first visit

  3. SSL/TLS

    TLS encrypts the connection and proves the site is really yours. Weak or expiring certificates trigger browser warnings and put traffic at risk.

    • High

      Weak SSL Key Length

      SSL certificate uses 256-bit key, which is considered weak

      What to do: Use at least 2048-bit RSA or 256-bit ECC key

      • CWE-326
      • OWASP A04:2025
      • Mozilla TLS: Mozilla Server Side TLS 6.0 intermediate: rsa_key_size 2048

Need hands-on remediation? Email guard@offseq.com

Keep watching substack.com

This scan found 18 issues across 6 checks. Monitoring re-runs those checks daily, emails you when something material changes and records each fix, so you can show progress.

Daily monitoring

Recommended

€25per month

  • TLS certificates and expiry
  • DNS records
  • SPF, DKIM and DMARC
  • Security headers
  • GDPR and NIS2 posture
  • Exposed services
  • Third-party trackers
  • Security score drift

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Results by check

Each check with its score, findings and the evidence it collected.

How this score is calculated

The security score runs 0–100, higher is better. It is the plain average of the security checks that completed in this scan, each counted equally. A check that could not run is left out: it counts neither as a pass nor as a fail.

Counted in this score

SSL/TLS
75
Security headers
45
Email security
85
DNS health
85
Network security
100
GDPR outside view
58
Average
75

Not counted

  • NIS2 outside view: Re-weights evidence from the TLS, email, DNS, network and hygiene checks, so counting it would count that evidence twice. Shown on its own.
  • OffSeq Observations: An AI reading of the site, useful context but not reproducible evidence. Shown on its own.

Findings that cap the score at 49

Each of these is serious on its own, so while any is present the site cannot rate better than high risk, however good the other checks are.

  • The certificate is not trusted by browsers
  • The website is not served over HTTPS
  • A database, remote desktop, file-sharing or Telnet service is reachable from the internet
  • The page loads a script from a compromised source
  • The domain registration has expired
  • SPF authorises every server to send mail as the domain

Partial scans

When the site blocks Guard or most checks cannot run, the score covers only the checks that ran (usually DNS and email), is capped at 75 and is shown as partial, without a risk level.

Risk levels

  • Critical0–25
  • High26–49
  • Medium50–75
  • Low76–100

Technical appendix

Business context, site observations and technical notes gathered during the scan, and the standards behind each reference.

Business context

Business profile

Substack holds a strong market position in the newsletter and subscription content space, leveraging a subscription-based business model that generates revenue from paid newsletters. The platform appeals to independent content creators and readers interested in niche and direct-to-audience content. The company is well-established since 2017 with a large user base and consistent branding. The absence of visible advertising and tracking suggests a focus on user experience and privacy, though explicit privacy compliance documentation is missing. Strategic partnerships or subsidiaries are not evident from the data provided.

Security posture

The website exhibits a mature security posture with HTTPS enabled and multiple security headers implemented, reducing common web vulnerabilities. No exposed sensitive data or vulnerable libraries were detected in the HTML content. However, the lack of published security policies, incident response contacts, or vulnerability disclosure mechanisms indicates room for improvement in transparency and readiness. Privacy compliance is weak due to missing privacy and cookie policies, which could expose the company to regulatory risks. Overall, the security posture is strong technically but incomplete in policy communication.

Recommendations

  1. Publish a comprehensive privacy policy and cookie policy accessible from all pages.
  2. Implement a cookie consent mechanism to comply with GDPR and other privacy regulations.
  3. Provide clear contact information including support and security incident response channels.
  4. Establish and publish a vulnerability disclosure policy or security.txt file.
  5. Enhance accessibility features to improve inclusivity and compliance with standards.
Site observations

Automated reading of the public site. Ratings are indicative.

Business

Company
Substack, Inc.
Description
Substack is a platform and app for independent voices, enabling writers and creators to publish newsletters and monetize their audience with full editorial control and ownership of intellectual property, mailing lists, and subscriber payments.
Key services
Newsletter publishing, Subscription management, Content hosting, Community engagement
Content quality
good
Branding
consistent

Technology

Stack
React, Tailwind CSS, Preact, WebP images, Modern font loading (woff2), Progressive image loading
Frameworks
React, Preact
Platforms
Web
Performance
fast
Mobile
good
Accessibility
basic
SEO
basic

Security

Observed score
90/100
Good practices seen
  • HTTPS enforced
  • Security headers present
  • No exposed sensitive data in HTML
  • No visible vulnerable libraries

Analytics and tracking

Tracking level
minimal
Privacy practices
poor

Advertising

Transparency
poor

Site quality

Design
good
User experience
good
Content relevance
good
Navigation
good
Professionalism
good
Trustworthiness
high

Key observations

  1. Website is fully accessible with no blocking or WAF challenges.
  2. No explicit privacy, cookie, or terms of service policies found in the HTML content.
  3. No contact emails, phone numbers, or physical addresses explicitly provided on the page.
  4. Modern web technologies and good security headers are implemented.
  5. Content is professional and targeted at independent content creators and readers.
  6. No advertising or tracking scripts detected in the provided HTML snippet.
  7. No vulnerability disclosure or security.txt files detected.
  8. WHOIS data confirms legitimate ownership by Substack, Inc.
Technical notes

Notes

The website uses a modern tech stack including React and Preact frameworks, Tailwind CSS for styling, and progressive image loading techniques with WebP format for performance optimization. Hosting leverages Amazon AWS S3 for media content delivery. The site is mobile optimized and loads quickly with valid HTML and CSS. SEO is basic with proper meta tags but could be improved with more structured data and sitemap inclusion. Accessibility is basic and could be enhanced. No legacy or vulnerable libraries were detected, indicating good maintenance and modernization.
Standards and sources

Reference chips under each finding point to the standard, regulation or specification the finding relates to. They are taken from the official datasets below and mapped conservatively: a finding with no defensible link shows none. NIS2 and GDPR references mark where a finding is relevant evidence, not a compliance verdict. Implementing Regulation (EU) 2024/2690 binds digital infrastructure and digital service providers; for other entities it is the most detailed public reading of the Article 21 measures. WCAG, EN 301 549, European Accessibility Act and Web Accessibility Directive references name the requirement an automated accessibility rule relates to; they are not a conformance verdict.

Retrieved 2026-10-25

Earlier scans of this domain

  1. 75/100Medium27 findingsView report
  2. 75/100 +1Medium27 findingsView report
  3. 74/100Medium23 findingsView report
  4. 74/100Medium23 findingsView report
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