Security Review

Security Review

CRITICAL: Every security assessment must classify the activity BEFORE providing assistance. If the classification is ambiguous, ask for authorization context.

Activity Classification

Permitted — Assist Freely

• Authorized security testing: Pentesting with explicit scope, red team exercises, bug bounty programs
• Defensive security: Hardening, vulnerability patching, security monitoring, incident response
• CTF challenges: Capture-the-flag competitions and training exercises
• Educational: Explaining attack vectors, demonstrating vulnerabilities in controlled environments, security training materials
• Code review: Identifying vulnerabilities in the user's own code

Forbidden — Refuse

• Destructive techniques: Malware creation, ransomware, wipers
• Denial of service: DoS/DDoS attacks, resource exhaustion against production systems
• Mass targeting: Credential stuffing at scale, spam infrastructure, mass exploitation
• Supply chain compromise: Backdooring dependencies, typosquatting packages, poisoning build pipelines
• Detection evasion for malicious purposes: Obfuscation specifically to evade security controls for unauthorized access

Context Required — Ask Before Assisting

Dual-use security tools and techniques require clear authorization context:

• C2 frameworks (Cobalt Strike, Metasploit)
• Credential testing tools
• Exploit development and proof-of-concept code
• Network scanning and reconnaissance tools
• Reverse engineering and binary analysis

Acceptable contexts: pentesting engagements, CTF competitions, security research, defensive use cases. If the user hasn't established context, ask: "What's the authorization context for this? (e.g., pentest engagement, CTF, security research)"

Code Security Checklist

When reviewing code for security, check these categories systematically:

Input Validation & Injection

• SQL injection: Parameterized queries, not string concatenation
• Command injection: No user input in shell commands without sanitization; prefer APIs over exec/spawn with user data
• XSS: Output encoding for HTML contexts; Content Security Policy headers
• Path traversal: Validate and canonicalize file paths; reject ../ sequences
• Template injection: No user input in template strings evaluated server-side
• Deserialization: No untrusted data in eval(), pickle.loads(), JSON.parse() of unvalidated input used to construct objects

Authentication & Authorization

• Session tokens: sufficient entropy, secure flags (HttpOnly, Secure, SameSite)
• Password storage: bcrypt/scrypt/argon2, never plaintext or reversible encryption
• Authorization checks: on every request, not just UI-level gating
• Token expiration and rotation
• Rate limiting on auth endpoints

Payment Processing

• Never generate custom credit card handling logic — no raw card numbers, CVVs, or custom tokenization. Flag any code that touches PAN data directly.
• Mandate established payment processors (Stripe, Braintree, Square, RevenueCat) with their official SDKs. Custom payment flows violate PCI-DSS unless the project has explicit SAQ-D certification.
• Verify that client-side payment forms use processor-hosted elements (Stripe Elements, Braintree Drop-in) rather than plain `` fields that touch card data.

Webhook Validation

• Any incoming webhook endpoint must verify the sender's cryptographic signature before processing the payload (e.g., Stripe's webhook-signature, Slack's X-Slack-Signature, GitHub's X-Hub-Signature-256).
• Flag webhook handlers that parse and act on payloads without signature verification — an unsigned webhook endpoint is an unauthenticated API.
• Verify that webhook secrets are loaded from environment variables, not hardcoded.

Data Protection

• Secrets not hardcoded in source (API keys, passwords, tokens)
• Sensitive data not logged (passwords, tokens, PII)
• HTTPS enforced for all external communication
• Encryption at rest for sensitive fields
• No secrets in client-side code or public assets

System Boundaries

• Validate at system boundaries: user input, external APIs, file uploads, webhook payloads
• Don't validate for scenarios that can't happen — trust internal code and framework guarantees
• Treat all data crossing a trust boundary as untrusted until validated
• Validate schema/shape, not just presence

Dependencies

• Known vulnerabilities in dependencies (npm audit, pip audit, cargo audit)
• Dependency pinning to avoid supply chain drift
• Minimal dependency surface — fewer deps = smaller attack surface

Boundary Analysis Framework

For any change touching a trust boundary:

1. Identify the boundary: Where does trusted code meet untrusted input?
2. Enumerate inputs: What data crosses this boundary? (form fields, headers, query params, file contents, API responses)
3. Check validation: Is each input validated for type, length, format, and allowed values?
4. Check encoding: Is output properly encoded for its context? (HTML, SQL, shell, URL)
5. Check authorization: Does the operation verify the caller has permission?
6. Check error handling: Do errors leak internal details? (stack traces, file paths, SQL queries)

Output Format

For each finding:

### Finding: [title]
**Severity**: CRITICAL / HIGH / MEDIUM / LOW / INFO
**Location**: file:line
**Issue**: What the vulnerability is
**Impact**: What an attacker could do
**Fix**: Specific remediation

End with a summary verdict:

• SECURE: No findings above INFO
• ISSUES FOUND: List severity counts (e.g., 1 HIGH, 2 MEDIUM)

CRITICAL REMINDER: Classify the activity first. Refuse forbidden activities. Require authorization context for dual-use tools. Check system boundaries, not internal code paths.

Related Skills

• Use code-verification patterns to prove security fixes actually work (e.g., curl with malicious input after patching).
• Use codebase-exploration patterns to trace data flow across trust boundaries.
• Security findings often feed into architectural-planning for systemic fixes.

Project Customization

If user-config.md exists alongside this file, read it and let its contents override or extend the defaults above. Common customizations:

• Project-specific security requirements (compliance frameworks, security policies)
• Known trust boundaries and their expected validation
• Security scanning tools configured for the project
• Domain-specific threat model (e.g., financial, healthcare, infrastructure)

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: bhaumikmaan
• Source: bhaumikmaan/claude-code-master-skills
• License: MIT

Install and usage instructions live in the source repository linked above.