> 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/dom/dom-based-cookie-manipulation.md).
# DOM-Based Cookie Manipulation
DOM-Based Cookie Manipulation notes for PortSwigger Web Security Academy labs, including exploitation workflow, payload testing, Burp Suite validation, and remediation context.
### DOM-based Cookie Manipulation
This lab shows a client-side manipulation (DOM) of cookies allowing to inject a value into the `lastViewedProduct` cookie. Changing this value can cause a content execution (XSS) on another page and call the `print()` function. Exploitation is done by directing the victim via the exploit server to the necessary pages.
* There is a session cookie named `lastViewedProduct` which contains the link of the last product viewed.
* On the page there is a "Last viewed product" section with an anchor such as `<a href=".../product?productId=1">Last viewed product</a>`.
* By altering the value stored as "last page view", the displayed link can be interpreted as HTML/JS.
* By replacing the cookie value with an external URL (`https://jord4n.pro`) the link redirects to this site.
The insertion of `JavaScript:print()` in the value is interpreted by the browser in this context.
* By injecting a payload containing HTML, for example `productId=1&'>
TEST
`, the content is rendered.
{% code overflow="wrap" %}
```html
Last viewed product
```
{% endcode %}
A scripting payload like `productId=1&'>` is also interpreted and triggered `print()`.
```
productId=1&'>
```
1. Store the victim in its `lastViewedProduct` cookie a value containing the injection (the product page is used to save this value).
2. Then direct the victim to the home page (or the page that displays "Last viewed product") so that the poorly formed value is returned and executes the script (`print()`).
3. Use the exploit server to orchestrate redirection to the product page (which writes the cookie) and then to the page where the cookie is displayed.
{% code overflow="wrap" %}
```javascript
```
{% endcode %}
---
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