avoid read/write access to ftp-root directory
The example proftpd.conf provided read/write access to the ftp-root directory
While directory-listing was disabled, it was still possible to upload files into the ftp-root directory ("/") and as well reading files from within this directory. But for this it required to know the exact filename of objects within the ftp-root directory.
The example proftpd.conf has been adapted to deny those actions.
If you are using this example-configuration, you should consider to update it!