/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/ is in live-image-xfce-desktop 4.0~a5-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/advanced.cfg
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/hdt.c32
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/install.cfg
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/ldlinux.c32
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/libcom32.c32
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/libutil.c32
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/live.cfg.in
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/menu.cfg
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/splash.svg
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/stdmenu.cfg
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/syslinux.cfg
/usr/share/live/images/xfce-desktop/config/bootloaders/syslinux/vesamenu.c32