Microsoft has a new Knowledgebase Article on UEFI SecureBoot DBX certs:
On July 29, 2020, Microsoft published security advisory 200011 that describes a new vulnerability that’s related to Secure Boot. Devices that trust the Microsoft third-party Unified Extensible Firmware Interface (UEFI) Certificate Authority (CA) in their Secure Boot configuration may be susceptible to an attacker who has administrative privileges or physical access to the device. This article provides guidance to apply the latest Secure Boot DBX revocation list to invalidate the vulnerable modules. Microsoft plans to push an update to Windows Update to address this vulnerability after further testing in 2021.[…]
https://uefi.org/revocationlistfile
There really should be more technical information provided about the revoked/otherwise bad certs in the DBX files.
Firmware Security 