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