UEFI defines a structured way to have data shared with OS as read write variables, including the ability to create, modify, and delete variables that UEFI can see.
However, some firmware used this facility to store values and then their code assumed the variables would always be there. The code would then crash when it goes to read a deleted variable and not know what to do. The thing is deleting those variables per spec is a perfectly valid the due the OS to do, but firmware was buggy and the bugs not caught because normally OS would not bother those variables except for a few standard popular ones, like boot order.
UEFI defines a structured way to have data shared with OS as read write variables, including the ability to create, modify, and delete variables that UEFI can see.
However, some firmware used this facility to store values and then their code assumed the variables would always be there. The code would then crash when it goes to read a deleted variable and not know what to do. The thing is deleting those variables per spec is a perfectly valid the due the OS to do, but firmware was buggy and the bugs not caught because normally OS would not bother those variables except for a few standard popular ones, like boot order.
I see, in that case, that would not be someone like me :P as I tend to care about specifications.
This is a really useful explanation for someone who doesn’t know about the UEFI spec.