Any account with normal shell access will have read access to "/" and any other world-readible directories like /etc/. This is normal, it's just how linux/unix works. What you want is a shell with chroot, but that's way easier said than done. I don't even think jailshell actually chroots the user, but I could be wrong on that. You'd probably need cloudlinux with CageFS to prevent shell/SFTP accounts from reading above their home directories. Keep in mind just because they can see something doesn't mean they can change anything.