A penetration test attestation letter is a short, signed document from your testing provider confirming that a test was performed — for whom, over what scope, when, using what methodology, and the high-level outcome, including that findings were remediated and retested where applicable. Unlike the full report (detailed, sensitive, internal-only), the letter is designed to be shared: it proves testing happened without exposing your exploitable weaknesses. It's what enterprise customers ask for during security reviews, what auditors accept as evidence, and often the single artefact that unblocks a stalled deal or closes out a compliance requirement.
// 01 What an attestation letter is
An attestation letter is the public-facing companion to your penetration test report. Where the report is a thick, detailed technical document meant only for your internal teams, the attestation is a one- or two-page letter from the testing provider that formally attests to the essentials: a test was carried out, for this client, over this scope, on these dates, to this methodology, with this high-level result — and that findings have been addressed. It carries the provider's name, credentials and signature, and it's built from the ground up to be handed to people outside your organisation.
// 02 Attestation letter vs full report
| Full Report | Attestation Letter | |
|---|---|---|
| Audience | Internal engineers & management | External — customers, auditors, partners |
| Detail | Every finding, evidence, repro steps, fixes | High-level summary only |
| Length | Tens of pages | 1–2 pages |
| Sensitivity | Highly sensitive (your weaknesses) | Safe to share |
| Purpose | Fix the issues | Prove testing happened |
The golden rule: the report goes to your team, the attestation goes to everyone else. Handing your full report to a prospect isn't diligence — it's disclosing your exploitable weaknesses to an outside party.
// 03 Why customers and auditors want one
Two forces drive demand for the attestation letter. First, enterprise sales: buyers' security teams increasingly require evidence of recent testing before signing, and the attestation is exactly the proof they need — without you exposing your report. Second, compliance: it's the artefact that evidences a testing requirement for SOC 2, PCI DSS, ISO 27001 or a regional regulator, and that an auditor can file. In both cases it answers "did you test, and did you fix what you found?" with a document that's safe to circulate. For many companies, producing the attestation on request is what turns a security review from a blocker into a formality.
// 04 What a good attestation letter contains
- Provider identity and credentials — who tested, and their qualifications.
- Client entity — who was tested.
- Scope — the systems or applications assessed, at a high level (no exploitable detail).
- Dates — when testing was performed.
- Methodology — the standards followed (PTES, OWASP, NIST).
- High-level outcome — the severity spread, and confirmation that findings were remediated and retested where applicable.
- Validity date and signature — how current the assurance is, and the provider's sign-off.
What it deliberately omits is any detail an attacker could use — specific vulnerabilities, evidence or reproduction steps. That omission is the whole point.
// 05 How to use it well
Treat the attestation letter as sales and compliance enablement. Keep a current one on hand (it needs to be recent to carry weight), and provide it the moment a prospect's security questionnaire asks for a pentest — fast turnaround here directly shortens deal cycles. File it as your compliance evidence for the relevant framework. And make sure it reflects a retested position: an attestation that confirms findings were remediated and verified is far stronger than one that just says a test occurred. If your provider doesn't offer an attestation letter as standard, ask — it's a normal deliverable, and one of the things worth confirming when choosing a provider.
// 06 Frequently asked questions
What is a penetration test attestation letter?
A short, signed document from the testing provider confirming a test was performed — for whom, over what scope, when, using what methodology, and the high-level outcome including that findings were remediated where applicable. It's a shareable summary that proves testing happened without exposing the sensitive detail of the full report.
Attestation letter vs penetration test report?
The report is the detailed, sensitive, internal-only technical deliverable. The attestation letter is a 1–2 page external summary that confirms the test occurred and the high-level result without disclosing exploitable detail. Report to your engineers; attestation to customers and auditors.
Why do customers ask for one?
Enterprise buyers require evidence of recent testing during vendor security reviews, but you can't hand them your full report of weaknesses. The attestation proves testing happened and issues were addressed, satisfying due diligence without creating risk — often unblocking a stalled deal.
What should it include?
Provider identity and credentials, client entity, high-level scope, testing dates, methodology (PTES, OWASP), a high-level outcome with severity spread, confirmation of remediation/retest where applicable, and a validity date and signature — with no exploitable specifics.
// 07 Related reading
- How to read a penetration test report — the detailed companion document.
- Your enterprise customer is asking for a pentest report — what they actually want.
- Retesting after remediation — what makes an attestation strong.