CVE-2022-40276 is a critical vulnerability found in Zettlr version 2.3., a popular open-source markdown editor used for note-taking and writing. This vulnerability allows an attacker to remotely obtain arbitrary local files on any client that attempts to view a malicious markdown file through Zettlr. The root cause of this vulnerability is the lack of a secure Content Security Policy (CSP) and improper validation of markdown contents before rendering them in the application.

Vulnerability Details

An attacker can craft a malicious markdown file containing an embedded HTML iframe tag with the src attribute pointing to a local file on the target user's machine, and then share the file with the victim. When the victim opens the markdown file using Zettlr, the application renders the iframe contents without proper validation, allowing the attacker to access the local file's contents.

Here is an example of a malicious markdown file containing an iframe element pointing to a local sensitive file:

# Malicious Markdown File

Please take a look at the following embedded content:

<iframe src="file:///etc/passwd" width="" height="" frameborder=""></iframe>

In this example, when the victim opens this file in Zettlr, the application will render the contents of /etc/passwd to the attacker-controlled iframe, allowing them to obtain sensitive information stored in that local file.

Affected Versions

Zettlr version 2.3. is affected by this vulnerability. It is recommended to upgrade to a newer version, in which the vulnerability has been fixed.

Mitigation and Patch

The patch developed by the Zettlr team resolves this issue by implementing a strict Content Security Policy (CSP) and properly validating the contents of markdown files before rendering them. To protect yourself from this vulnerability, it is recommended to update your Zettlr application to the latest version as soon as possible.

Users of Zettlr can download the latest version from the project's GitHub repository

- Zettlr GitHub Repository

To manually mitigate the vulnerability, users can refrain from opening untrusted markdown files from unknown sources. Alternatively, you may review markdown files in a plain-text editor before opening them in Zettlr to ensure no malicious code is embedded.

Conclusion

CVE-2022-40276 is a critical vulnerability in Zettlr version 2.3. that allows remote attackers to gain unauthorized access to sensitive local files through a maliciously crafted markdown file. Users are advised to update their Zettlr application to the latest version as soon as possible and exercise caution when opening untrusted markdown files.

Furthermore, developers and contributors to open-source projects such as Zettlr should always prioritize implementing proper security measures such as Content Security Policies (CSP) and validation mechanisms to protect the end-users from potential attacks.

For more information on this vulnerability and the patch, you may refer to the following resources

- CVE-2022-40276 - Zettlr Vulnerability
- Zettlr GitHub Repository and Changelog

Timeline

Published on: 11/03/2022 20:15:00 UTC
Last modified on: 11/05/2022 01:26:00 UTC