[princekolt]

Bad news: I tried the exploit in my macOS Sierra installation and it didn't seem to work. However, the passwd entry on the output of your first command IS A LONE ASTERISK.

However I still can't login as root. This leads me to believe this behavior has always been there, and maybe the login methods just didn't allow an empty password.

[ybloviator]

This is very normal in 'nix' systems. '' indicates a locked account. (I've given up figuring out how to escape an asterisk)

ex:

  daemon:*:1:1::0:0:Owner of many system processes:/root:/usr/sbin/nologin
  operator:*:2:5::0:0:System &:/:/usr/sbin/nologin
  bin:*:3:7::0:0:Binaries Commands and Source:/:/usr/sbin/nologin
  tty:*:4:65533::0:0:Tty Sandbox:/:/usr/sbin/nologin

If the OS is letting you in with a '*'in the encrypted password field, something is very very wrong.

[warent]

I'm confused, why do you have to escape an asterisk?

[HarfTarf]

He's stuck inside

[vsl]

Markdown in HN comments.

[royprins]

Famous last words of a Roman centurion.

[adrianratnapala]

Nah, I've never seen them do worse than knock people out. Probably the next thing the centurion said was "Ow, what hit me!".

[kr3wn]

wildcard.

[dep_b]

Only High Sierra is affected.