Linux dual-boot systems bricked by Secure Boot update

Microsoft pushed a Secure Boot Advanced Targeting (SBAT) update that was supposed to revoke old, vulnerable GRUB bootloaders. Instead, it bricked dual-boot Linux/Windows systems worldwide. Users who dared to run both operating systems were greeted with “Verifying shim SBAT data failed: Security Policy Violation” and an unbootable system. Microsoft had explicitly said the update “should not” affect dual-boot systems. It did.