Joplin is a free, open source note taking and to-do application. Joplin-desktop has a vulnerability that leads to remote code execution (RCE) when a user clicks on an <a> link within untrusted notes. The issue arises due to insufficient sanitization of <a> tag attributes introduced by the Mermaid. This vulnerability allows the execution of untrusted HTML content within the Electron window, which has full access to Node.js APIs, enabling arbitrary shell command execution.