> For the complete documentation index, see [llms.txt](https://hacking-notes.jord4n.pro/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://hacking-notes.jord4n.pro/web/cache-poisoning/url-normalization.md).
# URL Normalization
URL Normalization notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### URL Normalization
This lab contains a **XSS** vulnerability that is not directly exploitable, as the browser applies an automatic **dURL** encoding. / Therefore, the **Cache URL normalization process** must be used to exploit this flaw.
The goal is to inject a payload that runs `alert(1)` into the victim's browser and then provide it with the malicious URL.
#### 1) Injection Point Identification
When you access a non-existent page (e.g. `/test`), the site returns a **error page** that re-uses the requested path in the HTML response.
If an HTML tag is closed and a script is injected, it is interpreted as:
```javascript
/test
```
#### 2) Problem Encountered
If this URL is entered directly in the browser, the payload **n is not executed**. / The reason is that the browser **encodes automatically** special characters (`<`, `>`, `/`, etc.), which prevents script execution.
#### 3) Operation via Cache Standardization
To circumvent this protection, the **cache** is used:
* The malicious request is sent via **Burp Suite**, without going through the browser address bar.
* The cache **normalizes** URL and stores the associated response.
* The cached answer then contains the payload **unencoded**.
#### (4) Triggering the XSS
Once the answer is poisoned in the cache:
* The URL is provided to the victim.
* The cache returns the standard version of the page.
* The script is interpreted and `alert(1)` runs in the victim's browser.
---
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