Bypassing XSS Filters with Mavo Framework: A Technical Analysis

Cyber Security
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Bypassing XSS Filters with Mavo Framework: A Technical Analysis

Abstract

The Mavo framework, designed to provide a convenient way to access GET parameters, has inadvertently introduced a vulnerability that allows attackers to bypass XSS filters. In this paper, we will delve into the technical details of this vulnerability and demonstrate how it can be exploited to inject malicious JavaScript URLs into a website.

Introduction

The Mavo framework is a powerful tool for developers, allowing them to easily access GET parameters and create dynamic web applications. However, this convenience comes at a cost, as the framework’s design has introduced a vulnerability that can be exploited by attackers to bypass XSS filters.

DOM-Based XSS Vulnerabilities

The Mavo framework creates an object called $url, which provides a convenient way to access GET parameters. This object can be accessed using the $ syntax, as shown in the following example:

$url.x // get GET parameter x

However, this convenience also increases the likelihood that developers will introduce DOM-based XSS vulnerabilities. For example, if a developer uses the $url object to assign a href hyperlink object, they may inadvertently introduce a vulnerability that can be exploited by attackers.

Example Code

The following code snippet demonstrates how an attacker can inject a malicious JavaScript URL into a website:

<a href="{$url.spec}" mv-attribute="null" property="title"> </a>

In this example, the attacker injects a JavaScript URL that points to a relative path, which is then executed by the browser. The attacker can use this vulnerability to inject malicious JavaScript code into the website, bypassing XSS filters.

NoScript XSS Detection

The NoScript XSS detection mechanism is designed to prevent attackers from injecting malicious JavaScript code into a website. However, the Mavo framework’s design has introduced a vulnerability that can be exploited to bypass this detection mechanism.

Exploiting the Vulnerability

The attacker can exploit this vulnerability by using the fetch function to send a request to a remote server, which returns a JSON response that contains malicious JavaScript code. The attacker can then use the self.alert function to execute the malicious JavaScript code, bypassing the NoScript XSS detection mechanism.

MavoScript Abuse

The Mavo framework’s design has also introduced a vulnerability that can be exploited to bypass the NoScript XSS detection mechanism. The attacker can use the mv-expression attribute to define a custom delimiter, which can be used to inject malicious JavaScript code into the website.

Conclusion

The Mavo framework’s design has introduced a vulnerability that can be exploited to bypass XSS filters and inject malicious JavaScript code into a website. This vulnerability can be exploited by attackers to compromise the security of a website, and it is essential that developers and security researchers are aware of this vulnerability.

Recommendations

To mitigate this vulnerability, developers should:

  • Use the $url object with caution and ensure that it is properly sanitized to prevent XSS attacks.
  • Use the mv-expression attribute with caution and ensure that it is properly sanitized to prevent XSS attacks.
  • Implement additional security measures, such as Content Security Policy (CSP) and DOMPurify, to prevent XSS attacks.

By following these recommendations, developers can help to mitigate the risk of XSS attacks and ensure the security of their website.