# Penetration Testing Letters of Attestation **Published on:** 2026-05-12T00:00:00.000Z **Author:** null Organizations are increasingly asked to prove that their cybersecurity controls have been independently tested. Whether responding to customer security questionnaires, meeting vendor onboarding requirements, supporting compliance initiatives, or accelerating procurement reviews, companies often need a way to demonstrate that a penetration test was completed successfully without sharing the full report. This is where a penetration testing letter of attestation becomes valuable. A penetration testing letter of attestation is a formal document issued by a cybersecurity provider after a penetration test engagement. It confirms that testing occurred, outlines the scope at a high level, and summarizes the outcome of the assessment. While it does not replace a full penetration testing report, it provides external stakeholders with verification that security testing was performed by an independent party. For many organizations, especially SaaS providers, fintech companies, healthcare platforms, and enterprise vendors, a letter of attestation helps streamline trust conversations while protecting sensitive technical information. ## What is a Penetration Testing Letter of Attestation? A [penetration testing letter of attestation](https://cybri.com/blog/a-guide-to-penetration-test-letters-of-attestation/) is typically a concise document provided after the completion of a penetration test. It is intended for third-party sharing and acts as proof that a security assessment took place. The document often includes: * The name of the organization tested * The testing provider * The assessment dates * The scope of testing * The methodology used * A high-level summary of findings * Confirmation that identified issues were remediated or addressed, if applicable Unlike a full penetration testing report, the letter of attestation avoids exposing sensitive technical details such as exploit paths, screenshots, IP addresses, payloads, or infrastructure diagrams. This distinction is important because full reports can create additional risk if shared broadly with customers, vendors, or procurement teams. ## Why Organizations Use Letters of Attestation Many organizations face repeated requests for evidence of security testing. Sending a [complete penetration testing report](https://contact.packetlabs.net/cyber-maturity-assessment-sample-report-download) to every prospect or partner is rarely practical. A letter of attestation offers a middle ground between transparency and security. Common reasons organizations use penetration testing attestation letters include: ### Accelerating Vendor Security Reviews Enterprise procurement teams often require evidence of independent penetration testing before approving a vendor relationship. Instead of providing a full report, organizations can share a letter of attestation to demonstrate that testing was completed recently by a reputable provider. This can help reduce friction during: * Vendor onboarding * Procurement assessments * [Third-party risk management reviews](https://www.packetlabs.net/posts/third-party-risk/) * Security due diligence processes ### Protecting Sensitive Security Information Full penetration testing reports contain highly sensitive technical information that could increase organizational risk if mishandled. Sharing detailed reports externally may expose: * Network architecture * Application weaknesses * Authentication logic * Internal IP ranges * Security tooling * Exploitation methods A letter of attestation allows organizations to demonstrate diligence without unnecessarily disclosing exploitable information. ### Supporting Compliance and Regulatory Requirements Certain frameworks and industry standards require organizations to conduct regular penetration testing. A letter of attestation may help support evidence collection for: * [SOC 2 audits](https://www.packetlabs.net/posts/soc-2-attested/) * [ISO 27001](https://advisera.com/27001academy/what-is-iso-27001/) programs * [PCI DSS](https://www.packetlabs.net/posts/pci-dss-4-0/) requirements * [HIPAA security initiatives](https://www.hhs.gov/hipaa/index.html) * [Cyber insurance applications](https://www.packetlabs.net/posts/the-top-three-requirements-for-cyber-insurance-renewals/) * Internal governance reviews While auditors may still require direct access to reports in some situations, an attestation letter is often useful for preliminary documentation or customer-facing assurance. ### Building Customer and Client Trust Security-conscious customers increasingly expect vendors to demonstrate proactive cybersecurity practices. Providing a penetration testing attestation letter can reassure prospective customers that: * Security testing occurs regularly * Independent specialists performed the assessment * Findings were addressed appropriately * The organization takes cybersecurity seriously For [SaaS companies](https://www.packetlabs.net/industries/technology-and-saas/) in particular, this can strengthen trust during sales conversations. ## When Should You Request a Letter of Attestation? Not every penetration test automatically includes a letter of attestation. Organizations should discuss deliverables with their testing provider before the engagement begins. You should consider requesting a letter of attestation if: * Your customers routinely ask for proof of penetration testing * You frequently complete security questionnaires * Your organization undergoes [vendor risk assessments](https://www.packetlabs.net/posts/third-party-risk/) * You need external-facing proof of testing * You want to avoid distributing full reports widely * You support enterprise or regulated clients * You are preparing for compliance audits Organizations operating in highly regulated or enterprise-heavy markets often benefit the most from maintaining an up-to-date attestation letter. ## What a Good Letter of Attestation Should Include A strong penetration testing attestation letter should balance transparency with confidentiality. The document should clearly communicate that legitimate testing occurred while avoiding excessive technical disclosure. Typical components include: ### Assessment Overview This section identifies: * The client organization * The testing provider * Dates of testing * General assessment scope For example, the scope may reference: * External infrastructure * Internal network testing * Web application testing * Cloud environments * APIs * Mobile applications ### Methodology Reference Many attestation letters reference recognized methodologies or standards such as: * [OWASP Testing Guide](https://www.cloudflare.com/learning/security/threats/owasp-top-10/) * [NIST methodologies](https://www.nist.gov/cyberframework) * [PTES (Penetration Testing Execution Standard)](http://www.pentest-standard.org/index.php/Main_Page) This helps establish credibility and demonstrates that testing followed accepted industry practices. ### High-Level Findings Summary Rather than listing detailed vulnerabilities, the letter may summarize findings categorically. Examples include: * No critical findings identified * High-risk findings remediated * Medium-risk findings under review * Retesting completed successfully This provides stakeholders with assurance while minimizing unnecessary exposure. ### Testing Provider Validation The document should be issued on official company letterhead and include an authorized signature from the testing provider. This helps validate authenticity and supports trust during third-party reviews. ## Letter of Attestation vs. Full Penetration Testing Report Organizations sometimes confuse an attestation letter with the actual penetration testing report. The two documents serve different purposes. ### Full Penetration Testing Report A full report contains: * Technical findings * Exploitation evidence * Screenshots * Risk ratings * Reproduction steps * Remediation guidance * Detailed scope information This document is intended primarily for internal security teams and remediation stakeholders. ### Letter of Attestation A letter of attestation is a summarized verification document designed for external sharing. It focuses on: * Confirmation of testing * High-level results * Independent validation * Security assurance The goal is not to replace the report but to provide a safer and more practical document for broader distribution. ## Common Mistakes Organizations Make With Letters of Attestation Organizations sometimes undermine the value of a penetration testing attestation letter by making avoidable mistakes. ### Sharing Outdated Letters An attestation letter from several years ago may raise concerns rather than build trust. Many enterprise customers expect annual penetration testing at minimum, particularly for Internet-facing systems. ### Treating the Letter as a Compliance Shortcut A letter of attestation is not a substitute for remediation, secure development, or ongoing security practices. Stakeholders may still request additional documentation, especially in [regulated industries](https://www.packetlabs.net/industries-overview/). ### Using Generic or Vague Language A vague letter that provides little information may not satisfy procurement or security teams. The document should clearly establish: * What was tested * When testing occurred * Who performed the assessment * Whether issues were addressed ### Sharing Full Reports Unnecessarily Some organizations skip the attestation letter entirely and distribute complete penetration testing reports widely. This can create unnecessary security exposure and increase risk if the report is mishandled. ## Conclusion A penetration testing letter of attestation is an important tool for balancing transparency, trust, and security for key stakeholders. As vendor security reviews become more common, organizations increasingly need a way to demonstrate that independent penetration testing has occurred without exposing sensitive technical information. When used correctly, an attestation letter can: * Streamline procurement reviews * Support compliance initiatives * Improve customer and client trust * Reduce friction during security assessments * Protect confidential security details For organizations that regularly undergo vendor risk reviews or enterprise security assessments, maintaining an up-to-date penetration testing letter of attestation is becoming less of a nice-to-have and more of a standard business requirement.