ClickUp-MCP-Server

The codebase demonstrates strong security practices. It explicitly requires a `MASTER_KEY` environment variable for encryption of sensitive data (like ClickUp API keys), and validates it during startup, even refusing to start in production with insecure values. OAuth flows implement PKCE (Proof Key for Code Exchange) and enforce a configurable `REDIRECT_URI_ALLOWLIST`. Rate limiting is applied to API key issuance and OAuth endpoints. Secure cookie options (`httpOnly`, `sameSite: strict`, `secure`) are used. User-bound API keys expire after 30 days of inactivity. All API key comparisons use `timingSafeEqual` to prevent timing attacks. Robust logging is in place for requests and authentication failures. `app.set("trust proxy", true)` is correctly used for deployments behind a reverse proxy. The primary area for potential improvement is the broad `origin: "*"` CORS policy, although `credentials: false` mitigates some risks.