How to fix Security Misconfiguration
in Phoenix
Executive Summary
Phoenix applications often suffer from 'leaky' configurations where development-only tools like LiveDashboard or stack trace debuggers are exposed in production. Attackers leverage these to gain system telemetry, environment variables, or even RCE through session forging if the secret_key_base is weak or hardcoded. Hardening requires strict environment separation and robust secret management.
The Vulnerable Pattern
config :my_app, MyAppWeb.Endpoint, http: [port: 4000], debug_errors: true, code_reloader: true, check_origin: false, secret_key_base: "super-secret-but-hardcoded-value-123"router.ex
scope ”/” do pipe_through :browser live_dashboard “/dashboard” end
The Secure Implementation
1. Set debug_errors and code_reloader to false in production to prevent source code and environment leakage via crash reports. 2. Never hardcode secret_key_base; use System.fetch_env! to pull it from the environment at runtime. 3. Restrict LiveDashboard access by wrapping the route in a custom authentication plug (e.g., :authenticate_admin). 4. Enable force_ssl to ensure all traffic is encrypted and cookies are flagged as Secure. 5. Validate check_origin to prevent Cross-Site WebSocket Hijacking (CSWH).
config :my_app, MyAppWeb.Endpoint, http: [port: 4000], debug_errors: false, code_reloader: false, secret_key_base: System.fetch_env!("SECRET_KEY_BASE"), force_ssl: [rewrite_on: [:x_forwarded_proto]]router.ex
scope ”/” do pipe_through [:browser, :authenticate_admin] live_dashboard “/dashboard”, metrics: MyAppWeb.Telemetry end
defp authenticate_admin(conn, _opts) do if conn.assigns[:current_user] && conn.assigns[:current_user].is_admin do conn else conn |> redirect(to: ”/”) |> halt() end end
Your Phoenix API
might be exposed to Security Misconfiguration
74% of Phoenix apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.
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