Reflected XSS on 404 Error Page
By @gorkaRed social donde la pagina de error 404 refleja el parametro message en el HTML sin sanitizar, permitiendo XSS reflejado.
This hack was reported with no reward
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Credenciales
| Usuario | Contrasena | Rol |
|---|---|---|
| alice | password123 | user |
Despliegue
# Opcion 1: autodeploy
./autodeploy.sh
# Opcion 2: manual
docker compose up --build
# Acceder
http://localhost:1000
Compatible con macOS, Linux y Windows (Docker Desktop / WSL).
Para parar:
./autodeploy.sh destroy
# o: docker compose down -v
Contenido del Lab
La aplicacion
Chirp con pagina de error 404 que refleja un parametro de la URL.
La vulnerabilidad
La pagina 404 muestra ?message= directamente en el HTML sin escapar, permitiendo inyeccion de HTML y JavaScript.
Cadena de ataque
1. Visitar /404
2. Anadir ?message=<img src=x onerror=alert('XSS')>
3. XSS ejecutado
Solucion interactiva
Accede a /writeup dentro de la aplicacion para una guia paso a paso con botones interactivos.
Flag
(alert ejecutado)
Remediacion
- Escapar HTML en todos los outputs
- Usar textContent en vez de innerHTML
- CSP con nonces
