Which of the following best describes a Zero Day vulnerability?

A$.$

A zero$-$day vulnerability refers to a security flaw that has been discovered by a threat actor but is unknown to the enterprise and software vendor.

B$.$

A zero$-$day vulnerability refers to a security flaw that has been discovered but not mitigated by the software vendor.

C$.$

A zero$-$day vulnerability refers to a security flaw that has been discovered but not mitigated by the enterprise.

D$.$

A zero$-$day vulnerability refers to a security flaw that is a result of a system misconfiguration.