If you discover a security vulnerability in Secret, please report it privately via GitHub Security Advisories.

Do not open a public issue for security vulnerabilities.

We will acknowledge your report within 48 hours and aim to release a fix within 7 days for critical issues.

The following are in scope:

• Authentication bypass (PoW, API keys)
• Encryption/decryption flaws (key leakage, nonce reuse, plaintext exposure)
• Server-side access to plaintext content (zero-knowledge violation)
• SQL injection, path traversal, SSRF
• XSS, CSRF, header injection
• Rate limit bypass
• Information disclosure via error messages or timing side-channels

Secret uses a double-encryption model:

1. Client-side: XChaCha20-Poly1305 (libsodium) with keys derived via Argon2id
2. Server-side: AES-256-GCM (Node.js crypto) as defense-in-depth

The decryption key is stored in the URL fragment (#key), which browsers never send to the server. The server never has access to plaintext content.

• Timing-safe token comparison (crypto.timingSafeEqual)
• Key memory zeroing after use (sodium.memzero)
• Strict Content Security Policy (CSP)
• Per-IP rate limiting on all endpoints
• Zod validation on all inputs with max length constraints
• SQLite secure_delete and WAL mode
• Non-root Docker container with read-only filesystem
• No logging of note content, IPs, or user data

Only the latest version is supported with security updates.