You want to make sure that there are no world-writable directories in root's $PATH. To see why, read Adding the Current Directory to the $PATH.

Use this simple script to check your $PATH. Use it in conjunction with su -or sudo to check paths for other users:

#!/usr/bin/env bash
# cookbook filename: chkpath.1
# Check your $PATH for world-writable or missing directories

exit_code=0

for dir in ${PATH//:/ }; do
    [ -L "$dir" ] && printf "%b" "symlink, "
    if [ ! -d "$dir" ]; then
        printf "%b" "missing		"
          (( exit_code++ ))
    elif [ "$(ls -lLd $dir | grep '^d.......w. ')" ]; then
          printf "%b" "world writable	"
          (( exit_code++ ))
    else
          printf "%b" "ok		"
    fi
    printf "%b" "$dir
"
done
exit $exit_code

For example:

# ./chkpath
ok              /usr/local/sbin
ok              /usr/local/bin
ok              /sbinok /bin
ok              /usr/sbin
ok              /usr/bin
ok              /usr/X11R6/bin
ok              /root/bin
missing         /does_not_exist
world writable  /tmp
symlink, world writable /tmp/bin
symlink, ok /root/sbin

We convert the $PATH to a space-delimited list using the technique from Finding a File Using a List of Possible Locations, test for symbolic links (-L), and make sure the directory actually exists (-d). Then we get a long directory listing (-l), dereferencing symbolic links (-L), and listing the directory name only (-d), not the directory’s contents. Then we finally get to grep for world-writable directories.

As you can see, we spaced out the ok directories, while directories with a problem may get a little cluttered. We also broke the usual rule of Unix tools being quiet unless there’s a problem, because we felt it was a useful opportunity to see exactly what is in your path and give it a once-over in addition to the automated check.

We also provide an exit code of zero on success with no problems detected in the $PATH, or the count of errors found. With a little more tweaking, we can add the file’s mode, owner, and group into the output, which might be even more valuable to check:

#!/usr/bin/env bash
# cookbook filename: chkpath.2
# Check your $PATH for world-writable or missing directories, with 'stat'

exit_code=0

for dir in ${PATH//:/ }; do
    [ -L "$dir" ] && printf "%b" "symlink, "
    if [ ! -d "$dir" ]; then
        printf "%b" "missing				"
        (( exit_code++ ))
    else
        stat=$(ls -lHd $dir | awk '{print $1, $3, $4}')
        if [ "$(echo $stat | grep '^d.......w. ')" ]; then
            printf "%b" "world writable	$stat "
            (( exit_code++ ))
        else
            printf "%b" "ok		$stat "
        fi
    fi
    printf "%b" "$dir
"

done
exit $exit_code

For example:

# ./chkpath ; echo $?
ok              drwxr-xr-x root root /usr/local/sbin
ok              drwxr-xr-x root root /usr/local/bin
ok              drwxr-xr-x root root /sbin
ok              drwxr-xr-x root root /bin
ok              drwxr-xr-x root root /usr/sbin
ok              drwxr-xr-x root root /usr/bin
ok              drwxr-xr-x root root /usr/X11R6/bin
ok              drwx------ root root /root/bin
missing                         /does_not_exist
world writable drwxrwxrwt root root /tmp
symlink, ok            drwxr-xr-x root root /root/sbin
2