The problem doesn't like in magic open. The problem lies in assuming world writeable directories are safe. Consider the following program: 
foreach my $file (@ARGV) {
    open my $fh => ">", $file or die "Failed to open $file: $!\n";
    print $fh "Buzzle\n";
    close $fh or die "Failed to close $file: $!\n";
}

[download]

Or even: 

foreach my $file (@ARGV) {
    truncate $file, 0 or die "Failed to truncate $file: $!\n";
}

[download]

which doesn't even open a file, let alone use magic open. If you call any of those programs in a world writeable directory with * as argument as root, you're open for a DoS attack. All the attacker needs to do is create a symbolic link in the directory, pointing to an important file like /etc/passwd or /vmunix, and KABOOM!.

It would very insecure to think that using 3-arg open will fix your problems.

Abigail

In reply to Re: Dangerous diamonds! by Abigail-II
in thread Dangerous diamonds! by Juerd

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