Notesnook is a note-taking app. Prior to version 3.3.11 on Web/Desktop and 3.3.17 on Android/iOS, a stored XSS in the Web Clipper rendering flow can be escalated to remote code execution in the desktop app. The root cause is that the clipper preserves attacker-controlled attributes from the source page’s root element and stores them inside web-clip HTML. When the clip is later opened, Notesnook renders that HTML into a same-origin, unsandboxed iframe using "contentDocument.write(...)". Event-handler attributes such as "onload", "onclick", or "onmouseover" execute in the Notesnook origin. In the desktop app, this becomes RCE because Electron is configured with "nodeIntegration: true" and "contextIsolation: false". Version 3.3.11 Web/Desktop and 3.3.17 on Android/iOS patch the issue.