Pi-hole: file:// adlist read check and curl can resolve different files

Pi-hole is a DNS sinkhole that protects devices from unwanted content without installing any client-side software. Prior to 6.5, gravity.sh checks file:// adlist readability with sudo -u pihole test -r but then allows curl, sometimes running as root, to normalize URL dot segments and open a different file. A pihole-readable decoy can therefore pass the check while curl reads a root-only target, and /proc/self paths can similarly resolve against different processes. Exploitation requires an administrator who can add adlists and can place a symlink and decoy on the filesystem. This issue is fixed in version 6.5.