The /api/images/cache which is used to download media posters from the server accepted an url parameter, which was directly passed to the cache package and that downloaded the poster from this URL. This URL parameter can be used to make the jellysweep server download arbitrary content.

The API endpoint can only be used by authenticated users.

Fixed in v0.13.0. The affected (and now fixed) library was also moved to internal/ because it wasn't meant to be imported.