New Windows Zero-Day Flaw Disclosed by Researcher Gives Users System Rights

A researcher known as Nightmare Eclipse disclosed a vulnerability called SignDrop on Tuesday. The flaw affects certain versions of Windows and allows local users to achieve all-powerful System rights by forcing a privileged process like Windows Defender to open a specially crafted Common Log File System container. Ironically, the vulnerability stems from a security measure Microsoft introduced in October 2025 to prevent other CLFS exploits. By manipulating symbolic links, an attacker can cause Defender to trigger file creation in the context of the antimalware engine, effectively bypassing tampering protections and allowing privilege escalation.