GraphQL IDOR leads to information disclosure

Eshan Singh
Dec 24, 2019 · 3 min read

Hello World!, I’m Eshan Singh aka R0X4R. I’m here to share my recent findings on GraphQL IDOR (Insecure Direct Object Reference), which leads to information disclosure. So, let’s start. I’m signing in…

What is GraphQL?

The GraphQL Foundation defines “GraphQL is an open-source data query and manipulation language for APIs, and a runtime for fulfilling queries with existing data.” Nowadays, GraphQL is being used in place of Rest-API’s.


While doing recon for (A private program and as per their privacy policies, I cannot disclose their name), I found that the web app is using GraphQL for their API Management.

So, I firstly tried Introspection Query to extract sensitive information. After passing the query I saw a field called Users, so I pass

Query: {__type (name: \”Users\”) {name fields{name type{name kind ofType{name kind}}}}}”}

the query to enumerate the Types` definition in field “Users”, then I saw _type “Users” contains some fields i.e., Email, mobile_number, user_id, location, and api_key. So, I pass one more query to extract information those fields carried but I got 403 Unauthorised response.

Query: {Users{email,mobile_number,user_id,api_key}}

So, I thought that this web app is not vulnerable, so I started hunting for XSS. I clicked on My Profile, then I edited my name and intercepted the request, then I saw something interesting; the web app extracts previous info of the user before requesting a new edit.

Request: {“operationName”:”CurrentUserData”,”variables”:{“id”:” — base64 encode — “},”query”:”query CurrentUserData($id: ID!) {\n User(id: $id) {\n id\n email\n name\n mobile_number\n apiHostUrl\n SiteAdminUrl\n pages(first: 50) {\n nodes {\n id\n faviconUrl\n name\n code\n manageUrl\n __typename\n }\n __typename\n }\n __typename\n }\n}\n”}

So, I sent that request to the repeater and in that request, there is a variable called “id”, which contains something in base64. So, I decode that base64 encoded string

Decode: oph:cloud:redacted::user/p5yhwx30First Account: r0x4r@hhacker.comSecond Account:

“P5yhwx30” is my “id.” So, I created one more account on and copied its “id: oph:cloud:redacted::user/d5mzk1m2”.


Then I logged out from my second account and logged in with my first account. Now I pass the same query, but I changed my “id” with my second “id” and boom! I got the information.


But there’s a problem waiting for me that how I get another user “id.” So, after enumerating, I found that the “id” of the other users is in their profile page source code. I just have to go to their profile and view the source of their profile page, then I searched for “var_userID,” and I got their “id.”



Reported to on 15 Nov 2019

They rewarded me with 3 Digits bounty on 07 Dec 2019.

Thanks and regards!

Eshan Singh [R0X4R]

Signing out…

Eshan Singh

Written by

Hi.. I’m that hacker teenager that your friends told you about. I hack to make system secure. Hacker — Developer — Influencer — Graphics Designer

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