Stephen J. Bigelow has an article in TechTarget.com on VMWare and Secure Boot:
VMware vSphere 6.5 takes an extra security step, building on UEFI secure boot with added cryptographic validation to all ESXi components. VMware vSphere 6.5 added numerous features designed to improve the security of virtual machines both at rest and…[…]
You’ll have to give TechTarget.com your email address to read the article. 😦
http://searchvmware.techtarget.com/answer/How-does-ESXi-secure-boot-improve-vSphere-security
Firmware Security 