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There will be occasions where you can execute some limited javascript in a page. For example, in the case where you can[ **control a callback value that will be executed**](./#javascript-function).
In those case, one of the best things that you could do is to **access the DOM to call whatever** sensitive action you can find in there (like clicking a button). However, usually you will find this vulnerability in **small endpoints without any interesting thing in the DOM**.
In those scenarios, this attack will be very useful, because its goal is to be able to **abuse the limited JS execution inside a DOM from a different page from the same domain** with much interesting actions.
Basically the attack flow is the following:
* Find a **callback that you can abuse** (potentially limited to \[\w\\.\_]).
* If it's not limited and you can execute any JS, you could just abuse this as a regular XSS
* Make the **victim open a page** controlled by the **attacker**
* The **page will open itself** in a **different window** (the new window will have the object **`opener`** referencing the initial one)
* The **initial page** will load the **page** where the **interesting DOM** is located.
* The **second page** will load the **vulnerable page abusing the callback** and using the **`opener`** object to **access and execute some action in the initial page** (which now contains the interesting DOM).
{% hint style="danger" %}
Note that even if the initial page access to a new URL after having created the second page, the **`opener` object of the second page is still a valid reference to the first page in the new DOM**.
Moreover, in order for the second page to be able to use the opener object **both pages must be in the same origin**. This is the reason why, in order to abuse this vulnerability, you need to find some sort of **XSS in the same origin**.
* You can use this form to **generate a PoC** to exploit this type of vulnerability: [https://www.someattack.com/Playground/SOMEGenerator](https://www.someattack.com/Playground/SOMEGenerator)
* In order to find a DOM path to a HTML element with a click you can use this browser extension: [https://www.someattack.com/Playground/targeting\_tool](https://www.someattack.com/Playground/targeting\_tool)
* You can find a vulnerable example in [https://www.someattack.com/Playground/](https://www.someattack.com/Playground/)
* Note that in this example the server is **generating javascript code** and **adding** it to the HTML based on the **content of the callback parameter:**`<script>opener.{callbacl_content}</script>` . Thats why in this example you don't need to indicate the use of `opener` explicitly.
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