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Microsoft’s Secure Boot has been broken for a decade and no one noticed until now
(www.welivesecurity.com)
This is a most excellent place for technology news and articles.
Problem being, of course, that you can add more certificates, but you can't revoke the original M$ one. And since it's vulnerable and you can't get rid, then these exploits still work and there's nothing you can do to stop it.
Computers shouldn't come with Microsoft keys preinstalled to begin with (or an operating system for that matter). Microsoft being able to have Windows preinstalled on the vast majority of non-Apple PCs is how they gained their monopoly in the first place.
You should be able to remove any or all the certs as well, although I could see an argument for requiring you to enter the BIOS to do that.