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everything-claude-code/rules/web/security.md
2026-04-02 17:33:17 -07:00

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> This file extends [common/security.md](../common/security.md) with web-specific security content.
# Web Security Rules
## Content Security Policy
Always configure a production CSP.
### Nonce-Based CSP
Use a per-request nonce for scripts instead of `'unsafe-inline'`.
```text
Content-Security-Policy:
default-src 'self';
script-src 'self' 'nonce-{RANDOM}' https://cdn.jsdelivr.net;
style-src 'self' 'unsafe-inline' https://fonts.googleapis.com;
img-src 'self' data: https:;
font-src 'self' https://fonts.gstatic.com;
connect-src 'self' https://*.example.com;
frame-src 'none';
object-src 'none';
base-uri 'self';
```
Adjust origins to the project. Do not cargo-cult this block unchanged.
## XSS Prevention
- Never inject unsanitized HTML
- Avoid `innerHTML` / `dangerouslySetInnerHTML` unless sanitized first
- Escape dynamic template values
- Sanitize user HTML with a vetted local sanitizer when absolutely necessary
## Third-Party Scripts
- Load asynchronously
- Use SRI when serving from a CDN
- Audit quarterly
- Prefer self-hosting for critical dependencies when practical
## HTTPS and Headers
```text
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
Referrer-Policy: strict-origin-when-cross-origin
Permissions-Policy: camera=(), microphone=(), geolocation=()
```
## Forms
- CSRF protection on state-changing forms
- Rate limiting on submission endpoints
- Validate client and server side
- Prefer honeypots or light anti-abuse controls over heavy-handed CAPTCHA defaults