Ars Technica's Dan Goodin reports: Defenders across the world face the burden of responding to yet another botched code-execution vulnerability , this time in boot-time firmware used by most of the world's server vendors and data centers. The vulnerability, with a severity rating of 9.5 out of 10, resides in the TianoCore EDK II , an open source codebase that hardware makers and cloud providers use to create the UEFI firmware that runs during the boot-up sequence. Last year, a representative of the UEFI Forum called (PDF) EDK2 the "preeminent solution / implementation of the UEFI specifications." Virtually all UEFI suppliers (sometimes still called IBVs or independent BIOS vendors), including AMI, Insyde, and Phoenix, use the reference code extensively.…