Hubleys: Stored XSS via unrestricted background-image upload, served with an attacker-chosen Content-Type and no CSP protection

Hubleys is a dashboard for self-hosted services. Prior to version 0.5.2, any authenticated (non-admin) Hubleys user can upload a file with an arbitrary extension as their dashboard "background image," and the server will later serve that file back with a Content-Type derived straight from the attacker's chosen extension - so uploading an .html file gets it served as text/html. Because the endpoint that serves it returns a manually-constructed response rather than going through SvelteKit's normal page-rendering pipeline, the app's configured Content-Security-Policy never gets attached to it either, so a script embedded in the upload runs unrestricted. This issue has been patched in version 0.5.2.