Security headers

Skill hereshecodes/secureskills/skills/security-headers

Use when configuring HTTP responses, middleware, or server settingsFrom its SKILL.md

Install

npx -y skills add hereshecodes/secureskills --skill security-headers

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SKILL.md

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Security Headers

Every HTTP response should include security headers. They're your last line of defense and take minutes to add.

Related: xss-csrf, api-security, security-context

Rule 1: Content Security Policy (CSP)

Blocks inline scripts, unauthorized sources, and most XSS attacks.

// WRONG — no CSP (any script from anywhere can run)

// RIGHT — restrictive CSP
Content-Security-Policy: default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data: https:; font-src 'self'; connect-src 'self'; frame-ancestors 'none';

Rule 2: Strict-Transport-Security (HSTS)

Forces HTTPS. Prevents downgrade attacks.

// WRONG — no HSTS (browser may request HTTP first)

// RIGHT — enforce HTTPS for 1 year, include subdomains
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload

Rule 3: X-Content-Type-Options

Prevents MIME type sniffing. Browser respects the declared Content-Type.

X-Content-Type-Options: nosniff

Rule 4: X-Frame-Options

Prevents clickjacking by blocking your site from being embedded in iframes.

// Block all framing
X-Frame-Options: DENY

// Or allow only same-origin framing
X-Frame-Options: SAMEORIGIN

Rule 5: Referrer-Policy

Controls how much URL information is sent to other sites.

// WRONG — sends full URL including query params
Referrer-Policy: no-referrer-when-downgrade

// RIGHT — only sends origin, not full path
Referrer-Policy: strict-origin-when-cross-origin

Rule 6: Permissions-Policy

Restricts which browser features your site can use.

Permissions-Policy: camera=(), microphone=(), geolocation=(), payment=()

Implementation Examples

// Node.js / Express — use helmet
const helmet = require('helmet');
app.use(helmet());

// Or set manually
app.use((req, res, next) => {
  res.setHeader('X-Content-Type-Options', 'nosniff');
  res.setHeader('X-Frame-Options', 'DENY');
  res.setHeader('Referrer-Policy', 'strict-origin-when-cross-origin');
  res.setHeader('Permissions-Policy', 'camera=(), microphone=(), geolocation=()');
  res.setHeader('Strict-Transport-Security', 'max-age=31536000; includeSubDomains');
  next();
});

# Django — use django-csp and SecurityMiddleware
SECURE_HSTS_SECONDS = 31536000
SECURE_HSTS_INCLUDE_SUBDOMAINS = True
SECURE_CONTENT_TYPE_NOSNIFF = True
X_FRAME_OPTIONS = 'DENY'

Quick Reference

Header	Value	Purpose
Content-Security-Policy	`default-src 'self'`	Blocks unauthorized scripts/resources
Strict-Transport-Security	`max-age=31536000`	Forces HTTPS
X-Content-Type-Options	`nosniff`	Prevents MIME sniffing
X-Frame-Options	`DENY`	Prevents clickjacking
Referrer-Policy	`strict-origin-when-cross-origin`	Limits referrer info
Permissions-Policy	`camera=(), microphone=()`	Restricts browser features

What ships with it

Read from the repository

Just SKILL.md. No reference files, no scripts.

Gives 0 of the 12 instructions most security skills give in 759 tokens

Counted across 648 of the 828 authors here whose files we hold, read 2026-08-07

Parameterize all database queriesin 68 of 648, across 51 files
Hash passwords using bcrypt, scrypt, or argon2in 49 of 648, across 36 files
Apply rate limiting to authentication endpointsin 48 of 648, across 24 files
Configure security headersin 35 of 648, across 19 files
Validate all inputsin 32 of 648, across 24 files
Validate all external input at the system boundaryin 29 of 648, across 19 files
Run containers as a non-root userin 28 of 648, across 15 files
Use httponly secure samesite cookies for sessionsin 26 of 648, across 15 files
Run dependency audits before every releasein 21 of 648, across 10 files
Encode output to prevent cross-site scriptingin 21 of 648, across 11 files
Copy dependencies before source codein 20 of 648, across 9 files
Store secrets in environment variablesin 20 of 648, across 18 files

Said here and by no other author read

set the Strict-Transport-Security header to enforce HTTPS
use X-Frame-Options to block clickjacking
set the Referrer-Policy to limit referrer information
use Permissions-Policy to restrict browser features

Grouped from the skills themselves: near-identical wordings counted once, and counted by distinct author, so one author publishing three of these counts once. Length counted with cl100k_base; the agent that loads this file may tokenize it differently.