MX Linux Forum

AFAIK, this vulnerability is that BIOSConnect (an MS Windows application) trusts ANY wildcard certificate (not only dell's) from where to download BIOS updates.
So, ANYONE with a https wildcard certificate could download malicious "BIOS updates" on your computer.

But, BIOSConnect isn't for Linux ...

fehlix Linux Mint 20.1 Cinnamon (sha256sum: 14f73c93f75e873f4ac70b6cddc83703755c2421135a8fbbfd6ccfeed107e971)

Remove everything related to themes (and gfxmode) from /boot/grub/config/*.cfg >> rename /boot/grub/config/theme.cfg >> rename /boot/grub/theme (as nXecure said) >> replace starting of ...

OP may have meant "foobar" just as an example placeholder (almost like "John Doe" or "Jane Doe")
https://en.wikipedia.org/wiki/Foobar

In short, with "secure boot" on, MX boot rescue menus don't work at all to find EFI bootloaders .

Suggest to use MX/antiX LiveUSB Boot Rescue feature, which might do what you want to use it for: Find any attached EFI-/legacy grub loader/grub menus +plus WinOS loader and boot into.

fehlix I have dd'ed MX 19.4 , and enabled secure boot . Then, boot rescue menus can't detect any EFI bootloader ...

Just came back after a little experiment.

Tests performed on antiX Linux 19.3 Live USB (should be almost the same as MX Linux 19.X live USB)
Results: no "skewed" windows/EFI boot screen.

Steps:
0. No need to rename the mxlinux /boot/grub/theme/ folder.
1. Edit /boot/grub/grub.cfg. Comment out ...

fehlix It's not an installed Windows, but an Installer ( I've extracted the Windows ISO to an exFAT partition )

I am using grub from Linux Mint ISO (that plays better with SecureBoot, especially GRUB modules)

My setup is detailed in the first post of this thread https://forum.mxlinux.org ...

I want this USB to be used on any random machine coming to my friend's repair shop (will that require other steps?)
He is a Windows man who knows only GUI, and it would be good if everything works out of the box (on BIOS/EFI/SecureBoot etc.,)

Not sure what this thread is about. Suggest to use ...

Instead of LibreWolf, I use a sandboxed temporary firefox (with profile in RAM and cleared on exit) with some user.js changes too.

I use it for my normal browsing , and I have separately sandboxed (non-temporary) profiles for other things that require cookies (Email, forums etc.,)

I think a ...

rename the theme folder (/boot/grub/theme/) to something else (like theme-backup) and that should be enough. then it will be a very plain grub live boot.

Will that break anything ? (especially, the boot rescue menus shouldn't lose functionality)

the easiest way is to actually not use a theme ...