# Blind SSRF with out-of-band detection

## Lab Description

<figure><img src="/files/pcefAHJp2tDBLfeszSQ9" alt=""><figcaption></figcaption></figure>

## Step 1: Observing the Application

Upon accessing the lab, we're presented with a simple **store page** listing several products.&#x20;

<figure><img src="/files/Em3rp0MLfjWPxFvs78Ft" alt=""><figcaption></figcaption></figure>

Accessing any product we intercept the request using **Burp Suite**, and we see this HTTP request

This shows the `Referer` header is being set automatically.

<figure><img src="/files/eNhBbYGH66mZRroV8S7j" alt=""><figcaption></figcaption></figure>

## Step 2: Testing for Server-Side Interaction

Let’s test whether the application backend is **actually using** the `Referer` value in some way — for instance, calling or fetching it.

To do this:

1. Open **Burp Collaborator** and generate a unique payload (e.g., `https://.burpcollaborator.net`).
2. Modify the `Referer` header in the intercepted request to:

<figure><img src="/files/ZIB7RKNDYMvAD3EQrFO0" alt=""><figcaption></figcaption></figure>

## Step 3: Observing the Collaborator Interaction

Now, go to the **Burp Collaborator tab**.

You’ll observe that the application made both **DNS** and **HTTP** requests to your Burp Collaborator payload. This confirms that the backend has some analytics or tracking functionality that fetches the `Referer` URL server-side.

💡 **This proves that the `Referer` header is being processed by the server and used to initiate an outbound request.**


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