Specifically these issues: https://github.com/jellyfin/jellyfin/issues/5415
The big one is that video/audio playing endpoints can be used without authentication. However, you have to guess a UUID. If Jellyfin is using UUIDv4 (fully random), then this shouldn’t be an issue; the search space is too big. However, many of the other types of UUIDs could hypothetically be enumerated through brute force. I’m not sure what Jellyfin uses for UUIDs.
In the advanced class, we use orbital sanders.