Impact

The HTTP server does not set Content-Security-Policy, X-Frame-Options, or X-Content-Type-Options headers on any response. This reduces defense-in-depth against XSS, clickjacking, and MIME-sniffing attacks.

While the current XSS attack surface is small (React-markdown is configured safely, no dangerouslySetInnerHTML, Vite does not generate source maps), the absence of these headers means any future XSS vulnerability would have no secondary defense layer.

Affected code:

• packages/server/src/index.ts — all res.writeHead() calls only set Content-Type, with no security headers

Patches

Not yet patched.

Fix: Add security headers to all HTML/API responses:

res.writeHead(200, {
  "Content-Type": contentType,
  "Content-Security-Policy": "default-src 'self'; script-src 'self'; style-src 'self' 'unsafe-inline'; img-src 'self' data:",
  "X-Frame-Options": "DENY",
  "X-Content-Type-Options": "nosniff"
});

Workarounds

Use a reverse proxy (nginx, Caddy) in front of the Grackle server to inject security headers.

References

• CWE-693: Protection Mechanism Failure
• OWASP: HTTP Security Response Headers
• File: packages/server/src/index.ts