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Security report for substack.com

Substack · Technology · N/a

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 is a well-established platform founded in 2010 that empowers independent writers and content creators to publish subscription-based newsletters with full editorial control and ownership. The platform is positioned as a leader in the independent publishing space, offering key services such as newsletter publishing, subscription management, and reader engagement tools. The website demonstrates a professional design and consistent branding, targeting independent voices and readers interested in subscription content. Technically, Substack employs modern web technologies including React/Preact, Tailwind CSS, and Webpack, hosted on Amazon infrastructure with Cloudflare DNS and CDN services. The site is optimized for performance and mobile responsiveness, providing a good user experience. However, some SEO and accessibility features are basic, and there is room for improvement in these areas. From a security perspective, the site enforces HTTPS and uses domain status protections to prevent unauthorized changes. While no critical vulnerabilities or exposed sensitive data were detected, the absence of DNSSEC and explicit security policies or incident response information suggests opportunities to enhance security posture. Privacy compliance indicators such as privacy and cookie policies are not evident in the provided content, indicating a potential compliance gap. Overall, Substack presents a trustworthy and professional platform with a strong market position. Strategic recommendations include enabling DNSSEC, publishing comprehensive privacy and security policies, and adding vulnerability disclosure mechanisms to further strengthen trust and compliance.

Scanned

This is an earlier scan of substack.com. View the latest report

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

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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.

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  • 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 operates in the technology and media sectors, focusing on subscription-based newsletter publishing. Its business model revolves around enabling independent creators to monetize their content directly, bypassing traditional gatekeepers. The platform's competitive advantage lies in its ownership model, allowing creators to retain intellectual property and subscriber relationships. Revenue streams likely include subscription fees and possibly platform fees. The target audience includes independent writers, journalists, and readers seeking curated content. Growth indicators include a mature domain age and consistent branding. The partnership ecosystem includes Amazon for domain registration and Cloudflare for DNS/CDN services. The company maintains a medium size with a focus on technology-driven content delivery.

Security posture

Substack demonstrates a mature security posture with HTTPS enforcement and domain registration protections. The use of Cloudflare DNS adds a layer of security and performance. However, the lack of DNSSEC and absence of published security policies or incident response contacts indicate areas for improvement. No vulnerabilities or exposed sensitive data were found in the analyzed content. Compliance with GDPR and other privacy regulations is unclear due to missing privacy and cookie policies. The platform would benefit from publishing a security.txt file and vulnerability disclosure guidelines to enhance transparency and incident readiness. Overall, the security culture appears professional but could be more explicit in communication.

Recommendations

  1. Enable DNSSEC to improve DNS security and prevent spoofing.
  2. Publish comprehensive privacy and cookie policies with clear GDPR compliance statements.
  3. Add a security.txt file and vulnerability disclosure policy to facilitate responsible reporting.
  4. Implement and publicize an incident response policy and security contact channels.
  5. Enhance SEO and accessibility features to improve discoverability and inclusiveness.
Site observations

Automated reading of the public site. Ratings are indicative.

Business

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

Technology

Stack
React (implied by Preact Helmet usage), Webpack, Tailwind CSS, Cloudflare DNS, Amazon Registrar, Substack CDN
Frameworks
Preact, Tailwind CSS
Platforms
Web
Performance
fast
Mobile
good
Accessibility
basic
SEO
basic

Security

Observed score
80/100
Good practices seen
  • HTTPS enforced
  • Domain status includes clientDeleteProhibited, clientTransferProhibited, clientUpdateProhibited
  • No exposed sensitive data in HTML
  • Use of Cloudflare DNS for protection

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 content is fully accessible and not blocked by WAF.
  2. No explicit privacy, cookie, or terms of service policies found on the home page HTML provided.
  3. No contact emails or phone numbers explicitly found in the HTML content.
  4. Site uses modern web technologies and CDN for performance.
  5. No security.txt or vulnerability disclosure information found.
  6. No incident response or security contact information found.
  7. Content is professional and targeted at independent content creators.
  8. No suspicious or malicious content detected.
Technical notes

Notes

The website uses a modern tech stack including React/Preact, Tailwind CSS, and Webpack, served via a CDN (substackcdn.com) with DNS managed by Cloudflare. Hosting is supported by Amazon Registrar for domain management. The site loads efficiently with good mobile optimization and a professional UI. Some technical debt is suggested by the absence of DNSSEC and limited SEO metadata. The site lacks explicit security headers in the provided data, which could be improved. Overall, the infrastructure is robust and scalable but could benefit from enhanced security configurations and SEO optimizations.
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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