What's new? Hasn't JDownloader already served malware with the default installer for years, you had to use specific adware-free installers to avoid it?
Years ago I made my own "dark-ish mode" for it and holy hell, so annoying having to change 50 different more or less accurately labeled and named color settings that only take affect after restarting the program.
(https://claraiscute.neocities.org/Guides/jdownloader2/)
dark theme (https://github.com/moktavizen/material-darker-jdownloader)