Redmine, a popular web-based project management and issue tracking tool, recently unveiled a critical vulnerability (CVE-2023-47258) that has been identified in the Markdown formatter within Redmine versions before 4.2.11 and 5..x before 5..6. This vulnerability exposes Redmine users to dangerous Cross-Site Scripting (XSS) attacks that can have severe impacts on the confidentiality and integrity of their data. In this post, we will discuss the root cause of the issue, showcase a code snippet demonstrating the vulnerability, and provide details on how to reproduce the exploit, along with references to the original sources for a comprehensive understanding.

Understanding the Redmine XSS Vulnerability

Cross-Site Scripting (XSS) is a common web application security flaw that allows an attacker to inject malicious scripts into a trusted website or application. In Redmine, the specific vulnerability (CVE-2023-47258) lies within the Markdown formatter, where user input is not properly sanitized and escaped during the rendering process. This grants attackers the ability to craft input that, when parsed and displayed, executes arbitrary JavaScript code in the context of the Redmine application.

Code Snippet

Here is a code snippet that demonstrates the Redmine Markdown formatter processing user input without proper sanitization and escaping:

def markdown_text_to_html(text)

This method converts the given Markdown-formatted text (user input) into corresponding HTML using the Redmine Markdown renderer (@@markdown). However, it calls .html_safe on the rendered output, asserting that the output is safe and should not be escaped. As a consequence, unsanitized and unescaped content can slip into the rendered output and become the source of an XSS attack.

Reproducing the Exploit

The vulnerability can be exploited in any Redmine functionality that interprets and renders user-generated Markdown content. The following steps outline how to recreate the XSS exploit leveraging this vulnerability:

Log in to your Redmine instance using a user account with permissions to create or modify issues.

2. Find any issue or create a new one, then switch the issue description or comment text format to "Markdown" using the dropdown menu.

Save the input in the issue description or as a comment.

5. When other users view the page containing the saved content, the malicious script triggers an alert displaying "XSS" on their browser.

Original References

The XSS vulnerability in Redmine's Markdown formatter is well-documented within the official release notes and security advisories. Here are the links to these references:

- Redmine 4.2.11 release notes:
- Redmine 5..6 release notes:
- Redmine security advisory:
- Redmine GitHub commit resolving the vulnerability:

Closing Thoughts

Redmine's exposure to the XSS vulnerability (CVE-2023-47258) in its Markdown formatter underscores the importance of thoroughly sanitizing and escaping user input to prevent the injection of malicious scripts. The potential impacts of this vulnerability are significant, as it can compromise the confidentiality and integrity of Redmine's users and their data. As a Redmine user, it is essential to update your instances to version 4.2.11 or 5..6 immediately to protect your application from XSS attacks.


Published on: 11/05/2023 04:15:10 UTC
Last modified on: 11/14/2023 18:29:41 UTC