The recently discovered CVE-2023-23913 vulnerability poses a potential DOM based cross-site scripting (XSS) issue within the rails-ujs (unobtrusive JavaScript) library. This particular vulnerability targets HTML elements with the contenteditable attribute by leveraging the Clipboard API. Specifically, this issue occurs when users paste malicious HTML content from the clipboard, which includes a data-method, data-remote, or data-disable-with attribute. In this post, we will delve into the details of this vulnerability, providing code snippets, original references, and exploit details.

Code Snippet

Below is a simple code snippet that demonstrates how the vulnerability could be exploited. This example assumes that an attacker has managed to craft malicious HTML content with a data-method attribute and has pasted it within an element with the contenteditable attribute:

<!-- Example of a vulnerable contenteditable element -->
<div id="editable" contenteditable="true">
  <!-- Malicious HTML content with a data-method attribute -->
  <a href="#" data-method="delete" onclick="alert('XSS')">Click me to exploit</a>
</div>

For a detailed understanding of this vulnerability, refer to the following sources

1. Official CVE Details: CVE-2023-23913
2. Rails-UJS GitHub Repository: rails-ujs
3. Discussion Thread on the Vulnerability: Rails Confidential Issue

Exploit Details

The main exploitation scenario revolves around an attacker crafting malicious HTML content containing a data-method, data-remote, or data-disable-with attribute and managing to get a user to paste it within an element assigned the contenteditable attribute.

First, the attacker crafts the malicious HTML content, such as

<a href="#" data-method="delete" onclick="alert('XSS')">Click me to exploit</a>


2. Next, the attacker convinces the victim to paste the content into an element with the contenteditable attribute.

3. When the victim clicks on the pasted malicious content ("Click me to exploit"), it triggers the onclick event.

4. As a result, the attacker's injected script (in this example, alert('XSS')) executes, signifying a successful XSS attack.

Mitigation

To protect your applications from this vulnerability, consider implementing the following mitigation measures:

1. Update the rails-ujs library: Make sure to use the latest version of the rails-ujs library, as patches and updates are continually released to address vulnerabilities.

2. Sanitize user input: Implement server-side and client-side input validation to filter out potential XSS payloads.

3. Employ Content Security Policy (CSP): Configure a strong CSP to restrict the sources from which scripts can be executed within your application.

Conclusion

The CVE-2023-23913 vulnerability within the rails-ujs library showcases the importance of staying up-to-date with library patches, using secure coding practices, and employing robust security measures. To ensure your applications remain secure, keep abreast of new vulnerabilities and always follow security best practices.

Timeline

Published on: 01/09/2025 01:15:07 UTC
Last modified on: 01/09/2025 18:15:24 UTC