losetup maps a regular file to /dev/loop0 , allowing you to mount an ISO or ext4 image.
curl -I https://yourdomain.com/dev/d/ # If you get 200 OK and content-disposition or HTML listing, you are vulnerable. index of dev d
/dev stands for . It is a virtual directory created at boot time by the devtmpfs filesystem. It contains special files that represent hardware components and virtual devices connected to the computer. losetup maps a regular file to /dev/loop0 ,