CVE-2021-23447: Cross-site Scripting in teddy

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Background

Teddy is a readable and easy to learn templating language. It is an npm package used for generating dynamic HTML content. The package allows developers to create templates with placeholders that can be filled with data. These templates are then rendered to produce the final HTML output. Teddy is widely used in web development projects to simplify the process of generating dynamic web pages. However, versions of Teddy before 0.5.9 are vulnerable to a type confusion vulnerability that can be exploited to bypass input sanitization when the model content is an array instead of a string.

Vulnerability Detail

The vulnerability in Teddy arises from a type confusion issue. When the model content is expected to be a string but is provided as an array, the input sanitization process fails to properly handle the input. This can lead to a cross-site scripting (XSS) attack, where an attacker can inject malicious code into the generated HTML output. If an application using a vulnerable version of Teddy fails to properly sanitize user input, an attacker can exploit this vulnerability to execute arbitrary JavaScript code in the context of the victim's browser. This can result in various consequences, including unauthorized access to sensitive information, session hijacking, or defacement of web pages.

npm install teddy@0.5.9

Workaround

If updating Teddy to the latest version is not immediately feasible, developers can implement a workaround by manually sanitizing the model content before passing it to Teddy. This can be done by ensuring that the model content is always a string and removing any potentially malicious characters or code. Here's an example of how the workaround can be implemented in JavaScript:

const modelContent = JSON.stringify(userInput).replace(/[<>]/g, '');
teddy.render(template, JSON.parse(modelContent));

Conclusion

In conclusion, the vulnerability in Teddy allows for cross-site scripting attacks when the model content is an array instead of a string. Developers should update their Teddy package to version 0.5.9 or later to fix this vulnerability. If immediate update is not possible, a workaround can be implemented by manually sanitizing the model content. For further support on vulnerability remediation, you can contact DevNack.com.

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