New Windows Zero-Day Grants System Access

Security researchers released a Windows zero-day exploit named SignDrop that grants SYSTEM privileges by abusing Microsoft's October 2025 mitigation for the CLFS driver. The flaw affects 80% of Windows installations, including Windows 11 26H2 and Windows Server 2025 Experimental, allowing attackers to bypass antimalware engine self-defense mechanisms. Microsoft threatened legal action against the researchers.