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Just about every Windows and Linux device vulnerable to new LogoFAIL firmware attack
(arstechnica.com)
This is a most excellent place for technology news and articles.
The article quoted the researchers who indicated it can be done with remote access by using other attack vectors. This is because most UEFI systems store the logo on disk in the EFI system partition. It doesn't need to do anything crazy like compile and flash a modified firmware. All it needs to do is overwrite the logo file on disk.
If you have access to directly write to arbitrary disk locations you already have full control. Why bother with overwriting the logo file with a malicious payload if you can just overwrite the actual kernel...
Due to Secure Boot (if it actually enabled since there are some bogous implementations) this can be prevented. If I understand it correctly, LogoFAIL bypasses this security measure and enables loading unsigned code.