> 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/csrf/csrf-with-broken-referer-validation.md).
# CSRF with Broken Referer Validation
CSRF with Broken Referer Validation notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### CSRF with Broken Referer Validation
The site's email change feature tries to block cross-domain requests by checking the **Referer** header, but the detection logic is bypassable. The objective of the lab: to host on the server an HTML page that creates a CSRF to change the visitor's email address.
### Account to Be Used
* **User**: `wiener`
* **Password**: `peter`
If `Referer` comes from a different domain, the request is refused.
If the `Referer` header is missing, the check also fails (the request is refused).
* The validation is looking for a **match** containing a certain string in `Referer`. It therefore accepts a `Referer` which **contains** this string, even if there is additional text around.
* Example of accepted string detected:/ `https://JORD4N.PRO0aa7004f039e530680480331005c00f0.web-security-academy.net`
#### Bypass Observed
* Rather than sending the request from `/exploit`, the `Referer` can be made to contain the accepted string (e.g. by building a URL that includes this string).
/0aa7004f039e530680480331005c00f0.web-security-academy.net
* Browsers impose security restrictions that prevent arbitrarily sending certain forms of `Referer`. To force the full `Referer` from the exploit page, add the following meta-direction in ``:
```html
```
This directive tells the browser to send the URL of the full original page as `Referer` even when browsing cross-origin (unsafe behavior).
```html
```
---
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