Web Application Attack Surface Mapping

Systematically map a web application's content, entry points, technologies, and attack surface during authorized security testing or security-focused code review. Use this skill whenever you are performing reconnaissance on a web application, need to enumerate application functionality and hidden content, want to identify all user-input entry points (URLs, query parameters, POST fields, cookies, HTTP headers), need to fingerprint server-side technologies from HTTP responses, or are building an attack surface inventory before vulnerability testing. Also invoke it when analyzing application behavior to infer server-side structure, looking for undiscovered directories and files through brute-force enumeration, using search engines or web archives to find historical content, probing for hidden debug parameters, mapping functional paths in parameter-driven applications, or producing a behavior-to-vulnerability mapping that prioritizes which areas to probe first. Produces a structured attack surface map: enumerated URLs and functional paths, identified entry points, technology fingerprint, and a prioritized vulnerability-class checklist. Does not perform active exploitation — use this before any active testing phase.

Install

Claude CodeClawhHubnpxCursorCodexGemini CLI

1. Add marketplace

› /plugin marketplace add bookforge-ai/bookforge-skills

2. Install plugin

› /plugin install web-application-hackers-handbook@bookforge-skills

3. Use the skill

› /web-application-attack-surface-mapping

CC-BY-SA · Open sourceGitHub

Source Book

The Web Application Hacker's Handbook

Dafydd Stuttard and Marcus Pinto

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Systematically test web application access controls for broken authorization vulnerabilities. Use this skill whenever: performing a penetration test or security assessment of a web application's authorization model; testing for vertical privilege escalation (low-privilege user accessing high-privilege functions); testing for horizontal privilege escalation (user accessing another user's data); auditing multistage workflows for mid-flow authorization bypasses; checking whether protected static files are directly accessible without authorization; testing whether HTTP method substitution (HEAD, arbitrary verbs) bypasses platform-level access rules; probing for insecure access control models based on client-submitted parameters (admin=true), HTTP Referer headers, or IP geolocation; enumerating hidden or unlisted application functionality; reviewing source code or HTTP traffic for missing server-side authorization checks; using Burp Suite's site map comparison feature to compare high-privilege and low-privilege user access; assessing server-side API endpoint authorization. Covers all six WAHH vulnerability categories: completely unprotected functionality, identifier-based access control (IDOR), multistage function bypasses, static file exposure, platform misconfiguration, and insecure client-controlled access models. Maps to OWASP Testing Guide (OTG-AUTHZ-*), CWE-284 (Improper Access Control), CWE-285 (Improper Authorization), CWE-639 (Authorization Bypass Through User-Controlled Key), CWE-862 (Missing Authorization), CWE-863 (Incorrect Authorization), and OWASP Top 10 A01:2021 (Broken Access Control).

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Test web application business logic for vulnerabilities that automated scanners cannot detect. Use this skill when: performing a penetration test or security assessment and automated tools have been run but logic-layer coverage is still needed; testing multistage workflows (checkout, account creation, approval flows, insurance applications) for stage-skipping or cross-stage parameter pollution; probing authentication and password-change functions for parameter-removal bypasses (deleting existingPassword to impersonate an admin); testing numeric business limits for negative-number bypass (submitting -$20,000 to avoid approval thresholds); probing discount or pricing logic for timing flaws (add items to qualify, remove before payment); investigating whether shared code components allow session object poisoning across unrelated application flows; hunting for encryption oracles where a low-value crypto context can be used to forge high-value tokens; probing search functions that return match counts as side-channel inference oracles; testing for defense interaction flaws where quote-doubling plus length truncation reconstructs an injection payload; checking whether debug error messages expose session tokens or credentials cross-user via static storage; testing race conditions in authentication that cause cross-user session assignment under concurrent login. Logic flaws arise from violated developer assumptions — assumptions that users will follow intended sequences, supply only requested parameters, omit parameters they were not asked for, and not cross-pollinate state between application flows. Each flaw is unique and application-specific, but the 12 attack patterns documented here provide a reusable taxonomy that transfers across application domains. Maps to OWASP Testing Guide (OTG-BUSLOGIC-*), CWE-840 (Business Logic Errors), CWE-841 (Improper Enforcement of Behavioral Workflow), CWE-362 (Race Condition), and OWASP Top 10 A04:2021 (Insecure Design).

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Systematically assess web application authentication mechanisms for design flaws and implementation vulnerabilities. Use this skill whenever: testing the login security of a web application; auditing authentication for unauthorized access risk; evaluating password policy strength or brute-force resistance; checking whether login failure messages leak usernames (user enumeration); testing credential transmission over HTTP vs HTTPS; reviewing password change or forgotten password flows for logic flaws; assessing "remember me" cookie security; testing multistage login mechanisms for stage-skipping or cross-stage credential mixing; reviewing source code or HTTP traffic for fail-open logic or insecure credential storage; performing a penetration test or security code review of any user authentication system. Covers HTML forms-based, HTTP Basic/Digest, and multifactor authentication. Maps to OWASP Testing Guide (OTG-AUTHN-*) and CWE-287 (Improper Authentication), CWE-521 (Weak Password Requirements), CWE-307 (Improper Restriction of Excessive Authentication Attempts), CWE-640 (Weak Password Recovery Mechanism), CWE-312 (Cleartext Storage of Sensitive Information), CWE-522 (Insufficiently Protected Credentials).

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Test web applications for client-side security vulnerabilities spanning two major attack families: client-side trust anti-patterns and user-targeting attacks. Use this skill when: auditing hidden form fields, HTTP cookies, URL parameters, Referer headers, or ASP.NET ViewState for client-side data transmission vulnerabilities; bypassing HTML maxlength limits, JavaScript validation, or disabled form elements to probe server-side enforcement gaps; intercepting and analyzing browser extension traffic (Java applets, Flash, Silverlight) and handling serialized data; testing for cross-site request forgery (CSRF) by identifying cookie-only session tracking and constructing auto-submitting PoC forms; testing for clickjacking and UI redress attacks by checking X-Frame-Options headers and constructing iframe overlay proofs of concept; detecting cross-domain data capture vectors via HTML injection and CSS injection; auditing Flash crossdomain.xml and HTML5 CORS Access-Control-Allow-Origin configurations for overly permissive same-origin policy exceptions; finding HTTP header injection and response splitting vulnerabilities via CRLF injection; identifying open redirection vulnerabilities and testing filter bypass payloads; testing cookie injection and session fixation; assessing local privacy exposure through persistent cookies, cached content lacking no-cache directives, autocomplete on sensitive fields, and HTML5 local storage. Excludes XSS (covered by xss-detection-and-exploitation). Maps to OWASP Testing Guide (OTG-INPVAL-*, OTG-SESS-*, OTG-CLIENT-*), CWE-352 (CSRF), CWE-601 (Open Redirect), CWE-113 (HTTP Header Injection), CWE-565 (Reliance on Cookies), CWE-1021 (Improper Restriction of Rendered UI Layers), CWE-311 (Missing Encryption of Sensitive Data), and OWASP Top 10 A01:2021, A03:2021, A05:2021.