> For the complete documentation index, see [llms.txt](https://ganesha-hk.gitbook.io/cybersecurity-writeups/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ganesha-hk.gitbook.io/cybersecurity-writeups/port-swigger-graphql-labs/lab-2.md).

# lab-2

## Accidental Exposure of Private GraphQL Fields

**Difficulty:** Practitioner

### Lab Description

The user management functions for this lab are powered by a GraphQL endpoint. The API accidentally exposes user credential fields.

**Objective:** Sign in as the administrator and delete the user `carlos`.

### Solution

**Step 1 — Capture baseline traffic**

Access the lab, navigate to **My account**, and attempt a login with invalid credentials to generate traffic. Capture the requests in Burp Suite.

**Step 2 — Locate the GraphQL endpoint**

In the proxy history, find the `POST /graphql/v1` request that fires after the login attempt. Inspect it — it uses a GraphQL mutation for authentication. The schema details aren't visible from the mutation alone, so introspection is needed to understand the full API surface.

**Step 3 — Run an introspection query**

In Burp, go to **GraphQL > Set Introspection Query** and send it. Copy the returned JSON, then paste it into [GraphQL Visualizer](https://graphql-visualizer.netlify.app/) via **Change Schema → Introspection**. The schema diagram reveals a query named `getUser` that returns a `User` object — and the `User` type includes both `username` and `password` fields.

**Step 4 — Understand the query signature**

The raw introspection JSON shows the full definition of `getUser`:

```json
{
  "name": "getUser",
  "args": [
    {
      "name": "id",
      "type": {
        "kind": "NON_NULL",
        "name": null,
        "ofType": {
          "kind": "SCALAR",
          "name": "Int"
        }
      }
    }
  ],
  "type": {
    "kind": "OBJECT",
    "name": "User"
  }
}
```

This means `getUser` accepts a single non-null integer argument `id` and returns a `User` object.

**Step 5 — Construct a query to extract credentials**

Build a query using this signature:

```graphql
query getUser($id: Int!) {
    getUser(id: $id) {
        username
        password
    }
}
```

With the variable:

```json
{"id": 1}
```

**Step 6 — Retrieve the administrator's credentials**

Send the request. The response returns the administrator's username and plaintext password.

**Step 7 — Log in and delete carlos**

Log in using the administrator credentials. Navigate to the **Admin panel** and delete the user `carlos` to complete the lab.

### Conclusion

The `getUser` query was never intended to be part of the public API surface, but introspection was left enabled, allowing an attacker to discover it. The query exposed the `password` field without any access control checks, turning a schema design oversight into a full credential leak.


---

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