Web Application Penetration Testing Methodology: OWASP WSTG, PTES, NIST SP 800-115

Why Is a Methodology Needed?

A penetration test performed on a web application is not merely a matter of running security tools. When two different experts assess the same application, they can reach very different results if the methods used differ. A successful penetration test must therefore be based on a systematic, repeatable methodology aligned with international standards.

At SecureSys, we handle every web application penetration test within a defined plan: information gathering, identifying the attack surface, manual analysis, verification work, risk assessment and reporting.

International Standards

• OWASP Web Security Testing Guide (WSTG) — a comprehensive control framework for security testing of web applications.
• OWASP Top 10 — the reference for the most critical web application security risks.
• PTES (Penetration Testing Execution Standard) — a methodology that defines the penetration-testing life cycle.
• NIST SP 800-115 — a guide for technical security assessments of information systems.
• CVSS v4.0 — the standard used to score the technical risk of the vulnerabilities found.

The Web Application Penetration Testing Life Cycle

Planning → Information Gathering (Reconnaissance) → Attack Surface Analysis → Automated Security Scanning → Manual Security Testing → Business Logic Analysis → Risk Verification → CVSS Risk Assessment → Preparation of Technical and Executive Reports → Post-Remediation Verification (Re-Test)

1. Planning and Scope Definition

The boundaries of the test, target systems, critical business processes and the communication plan are clarified: Which domains will be tested? Are APIs in scope? Will the test be conducted with a Black Box, Gray Box or White Box approach?

2. Information Gathering (Reconnaissance)

Subdomains, open services, HTTP headers, certificates, JavaScript files, API endpoints and the technology stack (framework, CMS, server) are examined.

3. Attack Surface Mapping

Login screens, registration forms, file-upload modules, management panels, API services and user roles are mapped in detail.

4. Automated Security Scanning

Known vulnerabilities, security headers, misconfigurations and TLS/SSL configurations are scanned quickly. Automated scanning does not replace experts, but it helps determine where manual analysis should focus.

5. Manual Security Testing

The most important stage of the SecureSys approach. Our experts test authorization controls, authentication processes, business logic and API behaviour manually, from the perspective of a real attacker.

6. Risk Analysis and Prioritisation

Every finding is evaluated against criteria such as exploitability, business impact, data sensitivity, privilege requirement and detectability.

7. Technical Reporting and Executive Summary

For every finding, a description, technical details, proof of concept (PoC), risk level and remediation recommendations are reported; a summary for senior management is also prepared without overwhelming technical detail. See our deliverables page for details.

8. Remediation Verification (Re-Test)

After the organisation's remediation work, the relevant findings are re-tested and verified. The re-test is not the end of the process but part of a continuous improvement cycle.

Assessment Criteria

Assessment Criterion	Description
Exploitability	How easy is the vulnerability to exploit?
Business Impact	Which processes does the vulnerability affect?
Data Sensitivity	Which data is at risk?
Privilege Requirement	Does the attacker need prior privileges?
Detectability	Is exploitation of the vulnerability easily noticed?

To have your web application tested with a methodology aligned to international standards, reach out via our Web Application Penetration Testing Service page.