this bug appear when you set destination of backup in server folder,and it'll create INFINITELY like this:
Example: i choose plugins/AutoSaveWorld for destination
Then set the
pluginsfolder: true
in config.yml of ASW
Turn on the server and use /asw backup command,the plugin will create infinite folder _plugins/AutoSaveWorld/backup/day-time created of backup/_plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/plugins/AutoSaveWorld/backup/day-time created of backup/AND SOOO ON
UNTIL IT TRULY DESTROY THE HARD DRIVER, in my case, i luckily soon realized why it's took so long for a backup,i was /stop the server,you can see my latest log
latest.log
then i use disk defragment to regconize the damage it cause to my system,my C:/ is come from 0% fragmented into 19% after analyze,so this could kill a SSD driver very fast...

Please fix this bug!

A backup is to recover from incident, including when the server hardware fails. As such, a backup should be on a different physical disk, or preferably a different/remote storage.
There's already an option to ignore certain folders, have you tried it?

If there's an option to ignore duplicate files,you must do it better,terminate all possible error can cause to user,not by "because you don't read the instruction carefully" cause no one can read completely the instruction,so this is really a bug,an extremely dangerous bug can destroy everything,by the user "make mistakes"?You can't say that,how about a big server got hacked? He got Administrative and did that bug, would you just said "because you do not manage well"?

I understand you're extremely unhappy with your disk situation. I feel like you need to cool off and take the time to read my previous answer.
As for your security example, when you assume a hacker can change the plugin configuration, he/she can do way worse on your server then filling the freespace, in a much easier way than this specific plugin.