Security audit

Security Audit: Zero-Noise Vulnerability Assessment

Philosophy: Security findings must be actionable, not aspirational. Every finding requires a concrete exploit scenario — "an attacker could..." not "this might be vulnerable." Framework-aware scanning recognises built-in protections and doesn't flag them as missing. Zero-noise means developers trust the findings and act on them, instead of learning to ignore a wall of false positives.

Duration targets: BRIEF ~10-15 minutes (diff-only, focused scope), STANDARD ~20-40 minutes (full feature), COMPREHENSIVE ~40-60 minutes (full codebase section + threat model).

IMPORTANT: This skill is READ-ONLY. It never modifies code. It produces a report with findings and recommendations. Fixes are implemented by the developer or by returning to /execute.

Why This Matters

Security vulnerabilities in production code are among the most expensive defects to fix. The cost multiplier grows exponentially: a SQL injection caught in code review costs minutes; caught in penetration testing costs hours; caught after a breach costs reputation, legal fees, and customer trust. Automated security scanning catches the mechanical vulnerabilities that humans consistently miss — the ones hiding in plain sight.

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Trigger Conditions

Run this skill when:

• Before shipping features that handle authentication, authorisation, or user data
• Before shipping payment or financial processing features
• After /review and before /ship for any STANDARD+ scope feature
• User says "security audit", "security review", "check for vulnerabilities"
• Regulatory or compliance requirements mandate security review

Do NOT use for:

• Code quality review → /review
• Performance issues → different investigation
• Features with no security surface (pure UI styling, documentation)

Stage Gates — AskUserQuestion

At every PAUSE point in this skill, call the AskUserQuestion tool to present structured options to the user. Do not present options as plain markdown text — use the tool. The YAML blocks at each PAUSE point show the exact parameters to pass.

For pattern details and examples: ../_shared/references/stage-gates.md

Fallback: Only if AskUserQuestion is not available as a tool (check your tool list), fall back to presenting options as markdown text and waiting for freeform response.

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Mode Selection

Mode	When	Scope
BRIEF	Diff-only scan, small change	Only files changed since main. Quick OWASP check.
STANDARD	Full feature audit	All files in the feature. OWASP Top 10 + basic STRIDE.
COMPREHENSIVE	Pre-release, auth/payment features	Full OWASP + STRIDE threat model + dependency audit + ADR security review.

Scope modifiers (pass as part of the argument, e.g., "/security-audit auth diff-only"):

• diff-only — Only scan files changed since main (forces BRIEF)
• scope: {area} — Focus on specific area (auth, data, api, payment)
• owasp-only — OWASP Top 10 checklist only
• supply-chain — Dependency/supply chain audit only

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Collaborative Model

Phase 1: Scope & Context
Phase 2: Framework-Aware Scanning
Phase 3: STRIDE Threat Model (STANDARD+)
Phase 4: Findings & Report
  ── PAUSE 1: "Security audit complete. {N} findings." ──

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Prerequisites

Before starting, verify:

• Build succeeds (ensures code is parseable)
• Understand the tech stack (read CLAUDE.md for framework info)
• If upstream docs exist (PRD, design), note any security requirements or NFRs

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Critical Sequence

Phase 1: Scope & Context

Step 1.1 — Identify Target:

Determine what to scan based on mode and scope modifiers:

# BRIEF (diff-only)
git diff main --name-only

# STANDARD (feature files)
# Read execution manifest or locate feature directory

# COMPREHENSIVE (broad)
# All source files in affected services/projects

Step 1.2 — Identify Framework Protections:

Read the project's CLAUDE.md and identify built-in security protections from the tech stack. Understanding what the framework handles prevents false positives.

Identify framework protections (DO NOT flag these as missing):

Read the project's CLAUDE.md or equivalent to identify the tech stack. Then identify which security concerns are handled by the framework. Common patterns:

Protection Category	What to Look For	Example Frameworks
CSRF prevention	Anti-forgery tokens, SameSite cookies	ASP.NET Core, Django, Rails, Spring Security
Mass assignment prevention	DTO/model binding, allowed-field lists	ASP.NET Core model binding, Django forms, Rails strong params
Input validation pipeline	Framework-level request validation	FastEndpoints, Express-validator, Django REST serializers
SQL injection prevention	ORM parameterised queries	EF Core LINQ, Django ORM, SQLAlchemy, Hibernate
XSS prevention	Template auto-escaping, sanitisation	Angular templates, React JSX, Vue templates, Jinja2
Session management	Framework-managed sessions	ASP.NET Core Identity, Django sessions, Passport.js

If the project's framework handles a concern, verify it's correctly configured rather than flagging it as missing.

Step 1.3 — Identify Security Requirements:

If PRD or design docs exist, extract security-related requirements:

• Authentication requirements (who can access what)
• Authorisation rules (role-based, tenant-based, resource-based)
• Data protection requirements (encryption, PII handling)
• Compliance requirements (GDPR, HIPAA, SOC2)
• Security NFRs from the PRD

Record these — findings are more valuable when they reference violated requirements.

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Phase 2: Framework-Aware Scanning

Run through OWASP Top 10 (2021) checklist against the target files.

For each category, scan for vulnerabilities while respecting framework protections:

#	Category	What to Look For	False Positive Exclusions
A01	Broken Access Control	Missing auth attributes, direct object references, path traversal, CORS misconfiguration	Framework-provided auth middleware (if consistently applied)
A02	Cryptographic Failures	Hardcoded secrets, weak hashing, plaintext sensitive data, missing TLS	Framework-managed secrets (user-secrets, key vault references)
A03	Injection	Raw SQL, command injection, LDAP injection, template injection	EF Core LINQ queries, parameterised queries, Angular template binding
A04	Insecure Design	Missing rate limiting, no abuse case handling, business logic flaws	N/A — design issues are always reportable
A05	Security Misconfiguration	Debug endpoints in production, default credentials, unnecessary features enabled	Development-only configuration in appsettings.Development.json
A06	Vulnerable Components	Known CVE in dependencies, outdated packages, unmaintained libraries	N/A — always reportable
A07	Auth Failures	Weak password policy, missing brute-force protection, session fixation	Framework-provided identity (when correctly configured)
A08	Data Integrity Failures	Insecure deserialization, unsigned updates, CI/CD pipeline vulnerabilities	Framework-managed serialization (System.Text.Json with default options)
A09	Logging Failures	Missing security event logging, sensitive data in logs, no audit trail	N/A — logging gaps are always reportable
A10	SSRF	Unvalidated URLs in server-side requests, internal service discovery exposure	N/A — always reportable

Scanning discipline:

For each potential finding:

1. Verify it's real — Is this actually exploitable, or does the framework prevent it?
2. Confidence gate — Only report findings with confidence ≥ 8/10
3. Write the exploit scenario — "An attacker could {action} by {method} to {impact}"
4. Check for mitigations — Is there an existing mitigation that makes this lower risk?

DO NOT report these (common false positives):

1. Missing CSRF protection on API endpoints that use JWT (token-based auth doesn't need CSRF)
2. "Sensitive data in URL" for non-sensitive query parameters
3. Missing Content-Security-Policy on API-only services
4. "Hardcoded string" that is actually a configuration key name, not a secret
5. Missing rate limiting on internal-only endpoints
6. "Insecure direct object reference" when authorisation is checked by middleware
7. Missing input validation when the framework's validation pipeline is correctly configured
8. "SQL injection" in ORM-generated parameterised queries (EF Core LINQ, Django ORM, etc.)
9. Template expressions flagged as XSS when the framework auto-sanitises (Angular, React JSX, Vue, etc.)
10. Missing HTTPS in development-only configuration files

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Phase 2.5: Dependency Audit (COMPREHENSIVE only)

Skip in BRIEF and STANDARD modes.

Check project dependencies for known vulnerabilities:

1. Identify lock files — package-lock.json, yarn.lock, bun.lockb, *.csproj, requirements.txt, go.sum, Cargo.lock
2. Run audit commands — Use the project's package manager audit: npm audit, dotnet list package --vulnerable, pip audit, cargo audit
3. Check for outdated critical dependencies — security-relevant packages (auth libraries, crypto, HTTP clients) that are >2 major versions behind
4. Report findings — Only report vulnerabilities with a published CVE and a fix available

Phase 3: STRIDE Threat Model (STANDARD+)

Skip in BRIEF mode.

For each component in the feature, assess threats using STRIDE:

Threat	Question	Example Finding
Spoofing	Can an attacker pretend to be someone else?	Missing auth on endpoint, weak token validation
Tampering	Can an attacker modify data they shouldn't?	Missing integrity checks, direct DB access bypassing business rules
Repudiation	Can an attacker deny their actions?	Missing audit logging, no action attribution
Information Disclosure	Can an attacker access data they shouldn't?	Verbose error messages, missing authorisation on queries, PII in logs
Denial of Service	Can an attacker make the system unavailable?	Unbounded queries, missing pagination, resource exhaustion
Elevation of Privilege	Can an attacker gain higher access?	Role manipulation, tenant boundary bypass, admin endpoint without auth

Build a threat model table:

## Threat Model

| Component | Threat | Risk | Mitigation | Status |
|-----------|--------|------|-----------|--------|
| {endpoint} | Spoofing | High | Auth attribute required | ✅ Mitigated |
| {endpoint} | Info Disclosure | Medium | Authorisation check | ❌ Missing |
| {data store} | Tampering | High | Business rule enforcement | ✅ Mitigated |

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Phase 4: Findings & Report

Step 4.1 — Compile Findings:

Write the report to docs/reviews/security-audit-{timestamp}.md:

# Security Audit: {Feature Name}

> **Date:** {date}
> **Scope:** {BRIEF/STANDARD/COMPREHENSIVE} — {description of what was scanned}
> **Framework:** {tech stack from CLAUDE.md}
> **Files Scanned:** {count}

## Executive Summary

**Findings:** {count} ({critical}/{high}/{medium}/{low})
**Threat Model:** {STRIDE coverage if STANDARD+}
**Overall Risk:** {Critical / High / Medium / Low / Minimal}

## Critical Findings (Confidence ≥ 8/10)

### F1. {Title}
| Field | Value |
|-------|-------|
| **OWASP** | {A01-A10} |
| **STRIDE** | {S/T/R/I/D/E} |
| **Severity** | {Critical/High/Medium/Low} |
| **Confidence** | {8-10}/10 |
| **File** | `{path}:{line}` |
| **Exploit Scenario** | An attacker could {action} by {method} to {impact} |
| **Recommendation** | {specific fix} |
| **FR Reference** | {FR ID if applicable, or "N/A"} |

## Threat Model (STANDARD+)

{STRIDE table from Phase 3}

## Framework Protections Verified

| Protection | Status | Notes |
|-----------|--------|-------|
| {protection} | ✅ Active | {verification method} |

## Scope Limitations

This automated security audit is not a substitute for professional penetration testing.
It covers code-level vulnerabilities in the scanned files but does not cover:
- Infrastructure and network security
- Social engineering vectors
- Physical security
- Third-party service security posture
- Runtime configuration in production

PAUSE 1: Present the executive summary (finding count, severity breakdown, overall risk) as formatted markdown, then:

AskUserQuestion:
  question: "Security audit complete. {N} findings ({critical} critical, {high} high). How should we proceed?"
  header: "Security"
  multiSelect: false
  options:
    - label: "Review findings"
      description: "Walk through each finding in detail."
    - label: "Accept report"
      description: "Report saved. Address findings before shipping."
    - label: "Ship anyway"
      description: "Proceed to /ship despite findings (adds security warning to PR)."
    - label: "Fix critical"
      description: "Fix critical/high findings now, defer medium/low."

If "Review findings", present each finding individually using Guided Review (Pattern 5).

If "Fix critical", create targeted beads or return to /execute for critical/high findings.

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Anti-Patterns

Flag Everything — Reporting low-confidence findings "just in case" trains developers to ignore security reports. The confidence ≥ 8/10 gate exists because false positives destroy trust. A report with 3 real findings is infinitely more valuable than one with 3 real findings buried in 50 false positives.

Ignoring Framework Protections — Flagging "missing CSRF protection" on a JWT-authenticated API endpoint shows ignorance of how the framework works. Understanding built-in protections is prerequisite knowledge, not optional context. Read the framework docs before scanning.

Generic Recommendations — "Add input validation" is not actionable. Specify WHAT input, WHERE it enters, and HOW to validate it. Reference the specific file and line. Generic findings get ignored; specific findings get fixed.

Modifying Code — This skill is READ-ONLY. Never edit source files during a security audit. Findings go in the report; fixes go through /execute or direct development. Mixing audit and fix creates confusion about what was found vs what was changed.

Skipping Scope Limitations — Every security audit report MUST include the scope limitations disclaimer. Automated code scanning catches a subset of vulnerabilities. Presenting the audit as comprehensive security assurance is irresponsible and potentially dangerous.

Severity Inflation — A missing Content-Security-Policy header is not "Critical." Severity must match exploitability and impact. Critical means "exploitable now with significant impact." Reserve it for real emergencies — when everything is critical, nothing is.

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Exit Signals

Signal	Meaning	Next Action
No findings	Clean audit	Proceed to /ship
Findings reported	Issues found	Fix critical findings, then /ship
Critical findings	Serious issues	Fix before shipping — return to /execute
User accepts report	Acknowledged	Proceed to /ship (findings noted in PR)

When complete: "Security audit saved to docs/reviews/security-audit-{timestamp}.md. {N} findings. Address critical items before shipping."

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Skill Version: 1.0 v1.0: Initial release. OWASP Top 10 framework-aware scanning, STRIDE threat model, zero-noise reporting with confidence ≥8/10 gate, concrete exploit scenarios, 10 false positive exclusions, FR traceability, scope limitations disclaimer. Inspired by gstack's /cso zero-noise security audit.