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# Web Cache Poisoning via a Fat GET Request
Web Cache Poisoning via a Fat GET Request notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Web Cache Poisoning via a Fat GET Request
This lab is vulnerable to poisoning of the web cache because it accepts **GET requests with a body**, but **the body is not included in the cache key**. / A user regularly visits the home page of the site with Chrome. / The goal is to poison the cache so that the response runs `alert(1)` in the victim's browser.
**Initial analysis**
By intercepting the request to the home page, we observe the presence of the following cookie
Cookie: country=[object Object]
This cookie is generated from the JavaScript file loaded by the page:
```bash
/js/geolocate.js
```
**Analysis of `geolocate.js`**
Accessing the following directly:/ `/js/geolocate.js?callback=setCountryCookie`
The following code is obtained:
{% code overflow="wrap" %}
```javascript
const setCountryCookie = (country) => {
document.cookie = 'country=' + country;
};
const setLangCookie = (lang) => {
document.cookie = 'lang=' + lang;
};
setCountryCookie"({"country":"United Kingdom"});
```
{% endcode %}
We observe that:
* The `callback` parameter is used to define the function called.
* The passed value is then executed on the client side.
**Exploitation of vulnerability**
When loading the home page, the site automatically calls\:/ `/js/geolocate.js?callback=setCountryCookie`
By exploiting the fact that:
* The server accepts GET requests with a body.
* The body is not included in the cache key.
```bash
callback=alert(1)
```
We force a **new parameter `callback`** in the body of the GET request, giving it the following value:
The cached response now contains the call to `alert(1)`.
---
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