A code injection flaw exists in the WaveDrom rendering path of Markdown Preview Enhanced 0.8.x when used with crossnote 0.9.28. The flaw allows an attacker to inject malicious content into a fenced WaveDrom block inside a Markdown file. The unfiltered block content is passed to window.eval() in the VS Code webview context, enabling the execution of arbitrary JavaScript. Through the extension’s message passing system the attacker can issue file‑write commands on the local file system, compromising application integrity and confidentiality.

The vulnerability affects users of the Markdown Preview Enhanced extension for Visual Studio Code, specifically version 0.8.x, and the crossnote engine version 0.9.28 that provides the rendering functionality.

The CVSS base score of 8.4 indicates high severity, while the EPSS score is not available and the vulnerability is not listed in the CISA KEV catalog, suggesting no known active exploitation. Attackers can exploit this weakness by creating or modifying a Markdown document containing a malicious WaveDrom block, then opening the file in VS Code with the vulnerable extension installed. The exploit requires the user to be running the VS Code instance that hosts the extension, a typical privilege level for developers and end‑users.