Joplin is a free, open source note taking and to-do application, which can handle a large number of notes organised into notebooks. This vulnerability is caused by adding note titles to the document using React's `dangerouslySetInnerHTML`, without first escaping HTML entities. Joplin lacks a Content-Security-Policy with a restrictive `script-src`. This allows arbitrary JavaScript execution via inline `onclick`/`onload` event handlers in unsanitized HTML. Additionally, Joplin's main window is created with `nodeIntegration` set to `true`, allowing arbitrary JavaScript execution to result in arbitrary code execution. Anyone who 1) receives notes from unknown sources and 2) uses <kbd>ctrl</kbd>-<kbd>p</kbd> to search is impacted. This issue has been addressed in version 3.1.24 and all users are advised to upgrade. There are no known workarounds for this vulnerability.
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.