Notesnook vulnerable to RCE via stored XSS in Web Clipper rendering

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.