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# Parameter Cloaking
Parameter Cloaking notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Parameter Cloaking
This lab is vulnerable to **web cache poisoning** because a specific parameter is excluded from the cache key. / In addition, there is a **incoherence in the interpretation of parameters** between the cache system and the back-end. / A user regularly visits the home page of the site with **Google Chrome**.
Objective:/ Poison the cache using the **parameter cloaking** technique to run `alert(1)` in the victim's browser.
**Observation initiale**
The following cookie appears in the request:
```bash
Cookie: country=[object Object]
```
In the server response, a **geolocate** script is loaded. / This script uses the cookie value to define the user's country on the client side.
**Identification of the vulnerable parameter**
Using **Param Miner (Guess query params)**, we detect a behavior of **parameter cloaking**.
The parameter discovered is:
```bash
utm_content
```
If you access the following URL:
```bash
/?utm_content=z9qc51
```
We observe that:
* The parameter value can be freely changed
* The cache \*\* is not invalidated\*\*
* The answer remains the same for the following users
This confirms that `utm_content` is **excluded from the cache key**.
**Operation via geolocate script**
The script loaded by the page is:
```bash
/js/geolocate.js?callback=setCountryCookie
```
Adding the parameter ignored by the cache:
```bash
/js/geolocate.js?callback=setCountryCookie=test?utm_content=z9111
```
The following behavior is observed:
* The `test` value is reflected in the response
* The cache remains unchanged
This indicates that the back-end interprets the parameters differently from the cache.
**Injection via Parameter Cloaking**
This parsing difference is exploited by injecting a **second parameter callback** masked by `utm_content`:
```bash
/js/geolocate.js?callback=setCountryCookie&utm_content=z9111;callback=alert(1)
```
Outcome:
* The cache always considers the request identical
The backend interprets `callback=alert(1)` as a valid new parameter
The generated JavaScript runs `alert(1)`
---
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