MFA can be used to reduce the likelihood that the attacker gains access to the VM, however, the scenario specifically states that the attacker was able to escalate rights and the question asks what can be done to remediate the vulnerability. the vulnerability in this case would be the ability to escalate rights.
The best way to remediate the vulnerability is to update to the secure hypervisor version. A hypervisor is a software that creates and manages virtual machines on a physical server. A hypervisor can be vulnerable to various attacks, such as privilege escalation, code injection, or denial-of-service. Updating to the secure hypervisor version can help fix any known bugs or flaws in the hypervisor software and prevent attackers from exploiting them. Updating to the secure hypervisor version can also provide additional security features or enhancements that can improve the protection of the virtual machines and their data.