Which of the following best describes the vulnerability that was exploited in the Equifax cyber attack?

$1.$

The weakness was a malicious insder $-$ a vendor who had access to critical systems within the Equifax environment.

$2.$

The weakness was an unpatched vulnerability in an Equifax public$-$facing web server.

$3.$

The weakness was compromised credentials used by an attacker to gain unauthorized access to a system in the Equifax network

$4.$

The weakness was a phishing email sent to an Equifax employee where the adversary sent a malicious attachment over email.