A simple web application, that will reveal a secret code if you query using a command line tool like netcat, telnet or simpletcpclient.
Easiest way to run the vulnerable app is using docker-compose:
mkdir http-secret
cd http-secret
curl -o docker-compose.yml https://gitlab.cylab.be/cylab/play/http-secret/-/raw/main/docker-compose.yml
docker-compose up
After a few seconds, the app will be available at http://127.0.0.1:8000
docker run -p 8000:80 gitlab.cylab.be:8081/cylab/play/http-secret
You can use PHP built-in webserver to test locally:
git clone https://gitlab.cylab.be/cylab/play/http-secret.git
cd http-secret/src
php -S localhost:8000