security-review
FreeNo executable scriptsNot checkedSecurity code review for vulnerabilities. Use when asked to "security review", "find vulnerabilities", "check for security issues", "audit security", "OWASP rev
About this skill
Security Review Skill
Identify exploitable security vulnerabilities in code. Report only HIGH CONFIDENCE findings—clear vulnerable patterns with attacker-controlled input.
Scope: Research vs. Reporting
CRITICAL DISTINCTION:
- Report on: Only the specific file, diff, or code provided by the user
- Research: The ENTIRE codebase to build confidence before reporting
Before flagging any issue, you MUST research the codebase to understand:
- Where does this input actually come from? (Trace data flow)
- Is there validation/sanitization elsewhere?
- How is this configured? (Check settings, config files, middleware)
- What framework protections exist?
Do NOT report issues based solely on pattern matching. Investigate first, then report only what you're confident is exploitable.
Confidence Levels
| Level | Criteria | Action |
|---|---|---|
| HIGH | Vulnerable pattern + attacker-controlled input confirmed | Report with severity |
| MEDIUM | Vulnerable pattern, input source unclear | Note as "Needs verification" |
| LOW | Theoretical, best practice, defense-in-depth | Do not report |
Do Not Flag
General Rules
- Test files (unless explicitly reviewing test security)
- Dead code, commented code, documentation strings
- Patterns using constants or server-controlled configuration
- Code paths that require prior authentication to reach (note the auth requirement instead)
Server-Controlled Values (NOT Attacker-Controlled)
These are configured by operators, not controlled by attackers:
| Source | Example | Why It's Safe |
|---|---|---|
| Django settings | settings.API_URL, settings.ALLOWED_HOSTS |
Set via config/env at deployment |
| Environment variables | os.environ.get('DATABASE_URL') |
Deployment configuration |
| Config files | config.yaml, app.config['KEY'] |
Server-side files |
| Framework constants | django.conf.settings.* |
Not user-modifiable |
| Hardcoded values | BASE_URL = "https://api.internal" |
Compile-time constants |
SSRF Example - NOT a vulnerability:
# SAFE: URL comes from Django settings (server-controlled)
response = requests.get(f"{settings.SEER_AUTOFIX_URL}{path}")
SSRF Example - IS a vulnerability:
# VULNERABLE: URL comes from request (attacker-controlled)
response = requests.get(request.GET.get('url'))
Framework-Mitigated Patterns
Check language guides before flagging. Common false positives:
| Pattern | Why It's Usually Safe |
|---|---|
Django {{ variable }} |
Auto-escaped by default |
React {variable} |
Auto-escaped by default |
Vue {{ variable }} |
Auto-escaped by default |
User.objects.filter(id=input) |
ORM parameterizes queries |
cursor.execute("...%s", (input,)) |
Parameterized query |
innerHTML = "<b>Loading...</b>" |
Constant string, no user input |
Only flag these when:
- Django:
{{ var|safe }},{% autoescape off %},mark_safe(user_input) - React:
dangerouslySetInnerHTML={{__html: userInput}} - Vue:
v-html="userInput" - ORM:
.raw(),.extra(),RawSQL()with string interpolation
Review Process
1. Detect Context
What type of code am I reviewing?
| Code Type | Load These References |
|---|---|
| API endpoints, routes | authorization.md, authentication.md, injection.md |
| Frontend, templates | xss.md, csrf.md |
| File handling, uploads | file-security.md |
| Crypto, secrets, tokens | cryptography.md, data-protection.md |
| Data serialization | deserialization.md |
| External requests | ssrf.md |
| Business workflows | business-logic.md |
| GraphQL, REST design | api-security.md |
| Config, headers, CORS | misconfiguration.md |
| CI/CD, dependencies | supply-chain.md |
| Error handling | error-handling.md |
| Audit, logging | logging.md |
2. Load Language Guide
Based on file extension or imports:
| Indicators | Guide |
|---|---|
.py, django, flask, fastapi |
languages/python.md |
.js, .ts, express, react, vue, next |
languages/javascript.md |
.go, go.mod |
languages/go.md |
.rs, Cargo.toml |
languages/rust.md |
.java, spring, @Controller |
languages/java.md |
3. Load Infrastructure Guide (if applicable)
| File Type | Guide |
|---|---|
Dockerfile, .dockerignore |
infrastructure/docker.md |
| K8s manifests, Helm charts | infrastructure/kubernetes.md |
.tf, Terraform |
infrastructure/terraform.md |
GitHub Actions, .gitlab-ci.yml |
infrastructure/ci-cd.md |
| AWS/GCP/Azure configs, IAM | infrastructure/cloud.md |
4. Research Before Flagging
For each potential issue, research the codebase to build confidence:
- Where does this value actually come from? Trace the data flow.
- Is it configured at deployment (settings, env vars) or from user input?
- Is there validation, sanitization, or allowlisting elsewhere?
- What framework protections apply?
Only report issues where you have HIGH confidence after understanding the broader context.
5. Verify Exploitability
For each potential finding, confirm:
Is the input attacker-controlled?
| Attacker-Controlled (Investigate) | Server-Controlled (Usually Safe) |
|---|---|
request.GET, request.POST, request.args |
settings.X, app.config['X'] |
request.json, request.data, request.body |
os.environ.get('X') |
request.headers (most headers) |
Hardcoded constants |
request.cookies (unsigned) |
Internal service URLs from config |
URL path segments: /users/<id>/ |
Database content from admin/system |
| File uploads (content and names) | Signed session data |
| Database content from other users | Framework settings |
| WebSocket messages |
Does the framework mitigate this?
- Check language guide for auto-escaping, parameterization
- Check for middleware/decorators that sanitize
Is there validation upstream?
- Input validation before this code
- Sanitization libraries (DOMPurify, bleach, etc.)
6. Report HIGH Confidence Only
Skip theoretical issues. Report only what you've confirmed is exploitable after research.
Severity Classification
| Severity | Impact | Examples |
|---|---|---|
| Critical | Direct exploit, severe impact, no auth required | RCE, SQL injection to data, auth bypass, hardcoded secrets |
| High | Exploitable with conditions, significant impact | Stored XSS, SSRF to metadata, IDOR to sensitive data |
| Medium | Specific conditions required, moderate impact | Reflected XSS, CSRF on state-changing actions, path traversal |
| Low | Defense-in-depth, minimal direct impact | Missing headers, verbose errors, weak algorithms in non-critical context |
Quick Patterns Reference
Always Flag (Critical)
eval(user_input) # Any language
exec(user_input) # Any language
pickle.loads(user_data) # Python
yaml.load(user_data) # Python (not safe_load)
unserialize($user_data) # PHP
deserialize(user_data) # Java ObjectInputStream
shell=True + user_input # Python subprocess
child_process.exec(user) # Node.js
Always Flag (High)
innerHTML = userInput # DOM XSS
dangerouslySetInnerHTML={user} # React XSS
v-html="userInput" # Vue XSS
f"SELECT * FROM x WHERE {user}" # SQL injection
`SELECT * FROM x WHERE ${user}` # SQL injection
os.system(f"cmd {user_input}") # Command injection
Always Flag (Secrets)
password = "hardcoded"
api_key = "sk-..."
AWS_SECRET_ACCESS_KEY = "..."
private_key = "-----BEGIN"
Check Context First (MUST Investigate Before Flagging)
# SSRF - ONLY if U
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Allowed tools
Tools this skill is permitted to call.
ReadGrepGlobBashTaskBundled files
FAQ
What does the security-review skill do?
Security code review for vulnerabilities. Use when asked to "security review", "find vulnerabilities", "check for security issues", "audit security", "OWASP review", or review code for injection, XSS, authentication, authorization, cryptography issues. Provides systematic review with confidence-based reporting.
How do I install the security-review skill?
Copy the skill folder into ~/.claude/skills (the Claude Code tab above does this in one command), or install it as a plugin.
Does the security-review skill run scripts?
No, this skill is instructions only (SKILL.md) with no executable scripts.
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