Microsoft has faced legal warnings regarding the disclosure of vulnerabilities, but security researcher Nightmare Eclipse has revealed a new exploit called ShieldBreak that targets Windows Defender. This vulnerability allows attackers to escalate privileges from a low-level user account to full system access on Windows 10, Windows 11, and Windows Server 2025. The proof of concept for ShieldBreak is available as a downloadable application, requiring execution to activate the exploit. Security expert Will Dormann confirmed that Windows Defender must be activated for the attack to succeed. ShieldBreak builds upon a previous exploit named RoguePlanet, which Microsoft patched inadequately, allowing ShieldBreak to bypass the fix. Microsoft is currently investigating the reported vulnerability, but no patch has been released yet.