Microsoft has shared mitigations for YellowKey, a recently disclosed Windows BitLocker zero-day vulnerability that grants access to protected drives.

The security flaw was disclosed last week by an anonymous security researcher known as ‘Nightmare Eclipse,’ who described it as a backdoor and published a proof-of-concept (PoC) exploit.

Nightmare Eclipse said that exploiting this zero-day involves placing specially crafted ‘FsTx’ files on a USB drive or EFI partition, rebooting into WinRE, and then triggering a shell with unrestricted access to the BitLocker-protected storage volume by holding down the CTRL key.