Stored XSS in Post Body
By @gorkaRed social donde el cuerpo de los posts se renderiza con dangerouslySetInnerHTML, permitiendo XSS persistente que afecta a todos los usuarios que ven el post.
This hack was reported with no reward
Learn to find this bug
A real hack, reproduced for you to practice.
Create your account and practice real bugs that got paid. Download the environment, find it and learn the exact technique — your path to your first bounty.
hunters training
labs from real hacks
completions
paid out for these bugs
Access to all labs · no commitment · cancel anytime
Hackers who solved it· 8
Objectives
Achievement you'll earn
Solve this lab to unlock this shareable achievement
Community writeups
The checklist I run on every new target
47 checks ordered by cost: first what can get you in trouble, then the cheap stuff, and finally the expensive stuff — which is where the big bounties are. I'll send it to your inbox right now.
Unsubscribe in one click, from any email.
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 posts que soportan HTML en el cuerpo.
La vulnerabilidad
El cuerpo del post se renderiza con dangerouslySetInnerHTML sin sanitizacion. Cualquier HTML/JavaScript inyectado se ejecuta para todos los usuarios.
Cadena de ataque
1. Crear post con body: <img src=x onerror=alert('XSS')>
2. Publicar
3. Todos los que ven el post → XSS ejecutado
Solucion interactiva
Accede a /writeup dentro de la aplicacion para una guia paso a paso con botones interactivos.
Flag
(XSS persistente ejecutado)
Remediacion
- Sanitizar HTML con DOMPurify antes de renderizar
- Usar textContent o React JSX nativo
- CSP estricto
