Frontend Security

Frontend Security Audit Skill

Perform comprehensive security audits of frontend codebases to identify vulnerabilities, bad practices, and missing protections.

Audit Process

1. Scan for dangerous patterns - Search codebase for known vulnerability indicators
2. Review framework-specific risks - Check for framework security bypass patterns
3. Validate defensive measures - Verify CSP, CSRF tokens, input validation
4. Check dependencies - Review npm/node dependencies for vulnerabilities
5. Report findings - Categorize by severity with remediation guidance

Critical Vulnerability Patterns to Search

XSS Indicators (Search Priority: HIGH)

# React dangerous patterns
grep -rn "dangerouslySetInnerHTML" --include="*.jsx" --include="*.tsx" --include="*.js"

# Direct DOM manipulation
grep -rn "\.innerHTML\s*=" --include="*.js" --include="*.ts" --include="*.jsx" --include="*.tsx"
grep -rn "\.outerHTML\s*=" --include="*.js" --include="*.ts"
grep -rn "document\.write" --include="*.js" --include="*.ts"

# URL-based injection
grep -rn "location\.href\s*=" --include="*.js" --include="*.ts"
grep -rn "location\.replace" --include="*.js" --include="*.ts"
grep -rn "window\.open" --include="*.js" --include="*.ts"

# Eval and code execution
grep -rn "eval\s*(" --include="*.js" --include="*.ts"
grep -rn "new Function\s*(" --include="*.js" --include="*.ts"
grep -rn "setTimeout\s*(\s*['\"]" --include="*.js" --include="*.ts"
grep -rn "setInterval\s*(\s*['\"]" --include="*.js" --include="*.ts"

# Twig unescaped output
grep -rn "|raw" --include="*.twig" --include="*.html.twig"
grep -rn "{% autoescape false %}" --include="*.twig"

CSRF Indicators

# Forms without CSRF tokens
grep -rn "<form" --include="*.html" --include="*.jsx" --include="*.tsx" --include="*.twig"

# State-changing requests without protection
grep -rn "fetch\s*(" --include="*.js" --include="*.ts" | grep -E "(POST|PUT|DELETE|PATCH)"
grep -rn "axios\.(post|put|delete|patch)" --include="*.js" --include="*.ts"

Sensitive Data Exposure

# localStorage/sessionStorage with sensitive data
grep -rn "localStorage\." --include="*.js" --include="*.ts"
grep -rn "sessionStorage\." --include="*.js" --include="*.ts"

# Hardcoded secrets
grep -rn "api[_-]?key\s*[:=]" --include="*.js" --include="*.ts" --include="*.env"
grep -rn "secret\s*[:=]" --include="*.js" --include="*.ts"
grep -rn "password\s*[:=]" --include="*.js" --include="*.ts"

Reference Documentation

Load these references based on findings:

• XSS vulnerabilities found: See references/xss-prevention.md
• CSRF concerns: See references/csrf-protection.md
• DOM manipulation issues: See references/dom-security.md
• CSP review needed: See references/csp-configuration.md
• Input handling issues: See references/input-validation.md
• Node.js/NPM audit: See references/nodejs-npm-security.md
• Framework-specific patterns: See references/framework-patterns.md
• File upload handling: See references/file-upload-security.md
• JWT implementation: See references/jwt-security.md

Severity Classification

CRITICAL - Exploitable XSS, authentication bypass, secrets exposure HIGH - Missing CSRF protection, unsafe DOM manipulation, SQL injection vectors MEDIUM - Weak CSP, missing security headers, improper input validation LOW - Informational disclosure, deprecated functions, suboptimal practices

Report Format

## Security Audit Report

### Summary
- Critical: X findings
- High: X findings
- Medium: X findings
- Low: X findings

### Critical Findings

#### [CRITICAL-001] Title
- **Location**: file:line
- **Pattern**: Code snippet
- **Risk**: Description of the vulnerability
- **Remediation**: How to fix
- **Reference**: OWASP link

### High Findings
[...]

OWASP Reference Links

For comprehensive guidance, consult these OWASP cheatsheets directly:

• XSS Prevention: https://cheatsheetseries.owasp.org/cheatsheets/CrossSiteScriptingPreventionCheat_Sheet.html
• DOM XSS Prevention: https://cheatsheetseries.owasp.org/cheatsheets/DOMbasedXSSPreventionCheat_Sheet.html
• CSRF Prevention: https://cheatsheetseries.owasp.org/cheatsheets/Cross-SiteRequestForgeryPreventionCheat_Sheet.html
• CSP: https://cheatsheetseries.owasp.org/cheatsheets/ContentSecurityPolicyCheatSheet.html
• Input Validation: https://cheatsheetseries.owasp.org/cheatsheets/InputValidationCheat_Sheet.html
• HTML5 Security: https://cheatsheetseries.owasp.org/cheatsheets/HTML5SecurityCheat_Sheet.html
• DOM Clobbering: https://cheatsheetseries.owasp.org/cheatsheets/DOMClobberingPreventionCheatSheet.html
• Node.js Security: https://cheatsheetseries.owasp.org/cheatsheets/NodejsSecurityCheat_Sheet.html
• NPM Security: https://cheatsheetseries.owasp.org/cheatsheets/NPMSecurityCheat_Sheet.html
• AJAX Security: https://cheatsheetseries.owasp.org/cheatsheets/AJAXSecurityCheat_Sheet.html
• File Upload: https://cheatsheetseries.owasp.org/cheatsheets/FileUploadCheat_Sheet.html
• Error Handling: https://cheatsheetseries.owasp.org/cheatsheets/ErrorHandlingCheat_Sheet.html
• JWT Security: https://cheatsheetseries.owasp.org/cheatsheets/JSONWebTokenforJavaCheatSheet.html
• User Privacy: https://cheatsheetseries.owasp.org/cheatsheets/UserPrivacyProtectionCheatSheet.html
• gRPC Security: https://cheatsheetseries.owasp.org/cheatsheets/gRPCSecurityCheat_Sheet.html

Source & license

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

• Author: schalkneethling
• Source: schalkneethling/webdev-agent-skills
• License: MIT

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