ascii-art before 1.4.4 are vulnerable to command injection. This is exploitable when user input is passed into the argument of the
ascii-art preview command.
Example Proof of concept:
ascii-art preview 'doom"; touch /tmp/malicious; echo "'
Given that the input is passed on the command line and none of the api methods are vulnerable to this, the likely exploitation vector is when the ascii-art comment is being called programmatically using something like
Update to version 1.4.4 or later.