This document describes the security posture for KlarText.

The deployed system relies on:

1. CORS restrictions for browser-based access control
2. Per-IP rate limiting in production
3. Secret management for upstream providers such as Groq and OpenAI

┌─────────────────────────────────────────────────────────────────┐
│                       Current Request Flow                      │
├─────────────────────────────────────────────────────────────────┤
│                                                                 │
│   User → Frontend → Backend API                                 │
│                                                                 │
│   1. Browser sends request from an allowed origin               │
│   2. Backend enforces CORS policy                               │
│   3. Production traffic is rate limited per IP                  │
│                                                                 │
└─────────────────────────────────────────────────────────────────┘

The RateLimitMiddleware applies lightweight abuse protection in production:

• Skips /healthz for monitoring
• Skips OPTIONS requests for CORS preflight
• Is disabled entirely in development mode

Production requests are rate limited to reduce burst abuse:

• Limit: 30 requests per 60 seconds per IP address
• Response: HTTP 429 with Retry-After header
• Implementation: In-memory (resets on server restart)

For multi-instance deployments, consider Redis-backed rate limiting.

• Development: Allows all origins (*)
• Production: Restricted to origins in ALLOWED_ORIGINS

All endpoints use Pydantic models with:

• Maximum text lengths (40,000 chars for simplify, 5,000 for TTS)
• Pattern validation for language codes and levels
• File size limits (10MB for PDFs)

• All API calls go through src/lib/api.ts
• No auth token or API key is injected by the frontend helper
• No browser session storage is used for app access control

VITE_-prefixed variables are embedded in the JS bundle at build time.

The Chrome extension (apps/extension) communicates directly with the API using the same request model as the web frontend.

• Production traffic is rate limited
• CORS restricts browser-based cross-origin requests
• No raw user text is logged in analytics; only hashes are stored

• Anyone who can reach the API can call it; CORS only constrains browser-based access
• In-memory rate limiting resets on server restart
• CORS only constrains browsers; non-browser clients can still call the API directly

1. GROQ_API_KEY compromised:

   • Rotate the key in the Groq Console
   • Update the secret: fly secrets set GROQ_API_KEY=new_key

2. OPENAI_API_KEY compromised:

   • Rotate the key in the OpenAI dashboard
   • Update the secret: fly secrets set OPENAI_API_KEY=new_key

• Set ENVIRONMENT=production on Fly.io
• Configure ALLOWED_ORIGINS with your Vercel domain
• Test rate limiting against an API endpoint
• Ensure HTTPS is enforced

For security concerns, contact the KlarText team directly rather than opening a public issue.