KBID 285 - GraphQL IDOR

Running the app

$ sudo docker pull blabla1337/owasp-skf-lab:graphql-idor
$ sudo docker run -ti -p blabla1337/owasp-skf-lab:graphql-idor

Now that the app is running let's go hacking!

Running the app Python3

First, make sure python3 and pip are installed on your host machine. After installation, we go to the folder of the lab we want to practise "i.e /skf-labs/XSS/, /skf-labs/jwt-secret/ " and run the following commands:

$ pip3 install -r requirements.txt
$ python3 <labname>

Now that the app is running let's go hacking!

Docker Image and write-up thanks to defev!


As soon as we browse on we see that now our app implements a login screen to support multiple users

We already registered a user , the famous Jhon Doe and we can authneticate with the credentials


Now that we are in, we discover that every time a user logs in, the application sets a cookie called


that is used by the app to authenticate the keep the session active and recognize the user.

The API key can be used also to retrieve info from the blog. But this is another story.

What we want to do, is to find a way to authenticate us other users using an IDOR vulnerability.


What's new in this application is that an user can see his settings, browsing to the page:

of course only if authenticated. But how does this page retrieve the information is crucial. If we intercept the traffic we can see that the application sends a GraphQL query to the backend to ask for the information we see in the page. The query looks like this:

singleUser (user: 1)

Knowing that, use the IDOR vulnerability to authenticate as another user


Implement authorization on graphql endpoint. Although authenticated users could query the information, you should validate that the requestor of the information is actually the legit one, and use UUID instead of ID as Int.

Additional resources