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Security report for listerwindows.co.uk

Lister Windows · Manufacturing · United Kingdom

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

Security score

71/100

Risk levelMedium

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

Lister Windows is a well-established UK-based manufacturer and supplier specializing in uPVC and aluminium windows, doors, and conservatory roofs. With over 40 years of experience, the company targets professional window and door installers, commercial contractors, and housing developers across the UK. Their business model focuses on B2B trade partnerships, offering scalable solutions, fast lead times, and comprehensive trade support including quoting and marketing portals. The company holds reputable certifications and has a strong market position as an award-winning fabricator.

Scanned

NIS2 and GDPR posture

GDPR outside view
68/ 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"

    • High

      Missing Content-Security-Policy header

      Controls resources the browser is allowed to load

      What to do: Implement a Content-Security-Policy appropriate for your application

      • ASVS V3.4.3
      • OWASP Secure Headers: OWASP Secure Headers Project recommends Content-Security-Policy: default-src 'self'; form-action 'self'; base-uri 'self'; object-src 'none';…

  2. GDPR outside view

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

    • 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 listerwindows.co.uk

This scan found 21 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
30
Email security
85
DNS health
70
Network security
100
GDPR outside view
68
Average
71

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

Lister Windows operates in the manufacturing sector with a focus on trade supply. Their competitive advantages include a wide product range, fast and reliable delivery, and dedicated trade support services such as Easy Connect and Easy Marketing. The company maintains a strong partnership ecosystem, including subsidiaries Listers Central Ltd and GJB Developments Ltd, and collaborates with marketing partners like Full Circle Marketing. Their digital presence is professional and optimized for SEO, supporting growth and customer engagement.

Security posture

The website demonstrates a mature security posture with HTTPS enforced, presence of key security headers, and secure handling of forms. No critical vulnerabilities or exposed sensitive data were detected. However, the absence of a dedicated security policy or incident response page and lack of a vulnerability disclosure mechanism indicate areas for improvement. The use of third-party analytics and tracking scripts is balanced with privacy compliance measures including cookie consent and GDPR-aligned privacy policies.

Recommendations

  1. Publish a dedicated security policy and incident response information to enhance transparency and trust.
  2. Implement a vulnerability disclosure policy or security.txt file to facilitate responsible reporting.
  3. Regularly review and update third-party scripts to mitigate potential security risks.
  4. Enhance data retention disclosures related to analytics and tracking for improved privacy compliance.
  5. Continue to maintain and update certifications and trust indicators to reinforce market position.

Contact details published on the site

Addresses
Legal name
Listers Central Ltd
VAT number
GB 429 7730 64
Registration number
10948186
Site observations

Automated reading of the public site. Ratings are indicative.

Business

Company
Lister Windows
Description
Listers Trade suppliers, fabricating & supplying windows & doors to the trade for 40 years, delivery throughout the UK
Key services
Manufacture and supply of uPVC and Aluminium windows and doors, Conservatory roofing solutions, Trade support including quoting and ordering portals, Marketing support for trade partners
Content quality
excellent
Branding
consistent

Technology

Stack
WordPress, Yoast SEO plugin, Google Analytics, Microsoft Clarity, Google Tag Manager, Sentry, jQuery, WebP Express
Platforms
WordPress CMS
Performance
fast
Mobile
excellent
Accessibility
good
SEO
excellent

Security

Observed score
85/100
Good practices seen
  • HTTPS enforced
  • Security headers present
  • No exposed sensitive data in HTML
  • Use of secure forms
  • Third-party scripts asynchronously loaded

Analytics and tracking

Services
Google Analytics, Microsoft Clarity, Facebook Pixel
Tracking level
moderate
Privacy practices
good

Advertising

Tracking pixels
Microsoft Clarity, Facebook Pixel
Marketing tools
Easy Connect portal, Easy Marketing materials
Transparency
good

Site quality

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

Key observations

  1. Website is fully accessible with rich content and no blocking detected.
  2. Professional B2B manufacturing and supply business with strong trade focus.
  3. Comprehensive contact and legal information present.
  4. Good use of modern web technologies and SEO best practices.
  5. No security or privacy policy pages explicitly found beyond standard privacy and cookie policies.
  6. WHOIS data unavailable due to query error; domain likely 'listerwindows.co.uk' is registered and valid.
Technical notes

Notes

The website is built on WordPress CMS with modern plugins such as Yoast SEO and uses advanced technologies including Google Analytics, Microsoft Clarity, and Sentry for monitoring. The site is optimized for performance with WebP images and asynchronous script loading. Mobile responsiveness and accessibility are well addressed, contributing to excellent user experience. Hosting details are not explicitly identified but performance is fast. The technical stack supports scalability and effective digital marketing.
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

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