Syncthing is an open source, continuous file synchronization program. In versions prior to 1.23.5 a compromised instance with shared folders could sync malicious files which contain arbitrary HTML and JavaScript in the name. If the owner of another device looks over the shared folder settings and moves the mouse over the latest sync, a script could be executed to change settings for shared folders or add devices automatically. Additionally adding a new device with a malicious name could embed HTML or JavaScript inside parts of the page. As a result the webUI may be subject to a stored cross site scripting attack. This issue has been addressed in version 1.23.5. Users are advised to upgrade. Users unable to upgrade should avoid sharing folders with untrusted users.
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.