This metric captures the requirement for a human user, other
than the attacker, to participate in the successful compromise
of the vulnerable component.
Values:
USER_INTERACTION_UNSPECIFIED (0):
Invalid value.
USER_INTERACTION_NONE (1):
The vulnerable system can be exploited
without interaction from any user.
USER_INTERACTION_REQUIRED (2):
Successful exploitation of this vulnerability
requires a user to take some action before the
vulnerability can be exploited.