Chevereto is a self-hosted media-sharing platform. Starting in version 3.7.5 and prior to version 4.5.4, when a user enables the private profile option, visiting their profile HTML route ("/username") correctly returns 404. However, the "/json" AJAX listing endpoint does not apply the same check. An unauthenticated caller who knows the target's user ID can retrieve all of that user's publicly-scoped images, revealing the username (which should be private). This is patched in Chevereto v4.5.4. No known workarounds are available.