Microsoft’s Secure Boot has been broken for a decade and no one noticed until now
(www.welivesecurity.com)
No.
Secure Boot is basically a 'lock', on the UEFI.
UEFI - Shim is basically a 'lockpick'.
UEFI is the first step in your computer booting, turning on.
So, if Secure Boot is supposed to be a 'lock', that limits who can access the UEFI ... but it turns out that there are many, old, UEFI - Shims, that defeat that 'lock'... then Secure Boot is not a good 'lock'.
I don't mean to be rude but it seems like there might be a bit of language confusion going on here... In English, a 'shim' is a kind of crude/simple tool that can be used to break or bypass some actual physical locks.
So 'UEFI-Shim' basically means 'a thing that breaks into your UEFI'.