Once I have found that searsh systems indexed much more pages on my site. I tryed to analize this and found that if a directory listing exists on a /node/398/ I can enter any random number such as /node/398/1292877 wait 5-10 seconds and see some system directory listing, that I can't find on server, seems it is forbidden, but filebrowser get access to it. Another random adresses, such as /node/398/91227563 must show error404, but show main directory listing with error "Notice: Undefined index: path in function _filebrowser_load_files() (row 289 in file /var/www/vhosts/63/156765/webspace/httpdocs/led-displays.ru/sites/all/modules/filebrowser/filebrowser.common.inc)." Screenshots attached in bug report, but seems due to my account status, bug issue not published yet - https://www.drupal.org/node/2904248.