> 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/web-cache-poisoning-with-unkeyed-cookie.md).
# Cache Poisoning with an Unkeyed Cookie
Cache Poisoning with an Unkeyed Cookie notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### Web Cache Poisoning with an Unkeyed Cookie
This lab is vulnerable to web cache poisoning as cookies are not included in the cache key. A legitimate user regularly visits the home page. / The goal is to poison the cache with a response that executes `alert(1)` in the victim's browser.
#### Analysis of the Response
* The request is intercepted to the root (`/`).
* In the HTML response, we observe a JavaScript script containing dynamic data:
```javascript
```
* The `frontend` field is the value of a cookie sent by the browser
#### Cookie Observation
* In the query, a cookie named `fehost` is present:
```bash
fehost=prod-cache-01
```
* This value is reused directly in the response without being integrated into the cache key.
#### Cookie Manipulation
* By changing the value of the `fehost` cookie, the answer immediately reflects the new value:
```bash
fehost=test
```
* This confirms that the cookie is **not indexed in the cache** and that it influences the cached content.
#### Payload Injection
* A malicious value is then injected into the cookie to break the JavaScript context and execute arbitrary code:
```javascript
test"-alert(1)-"efffe
```
* Payload escapes from the JavaScript string and injects a call to `alert(1)`.
---
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