Nightmare Eclipse Releases ShieldBreak, a Critical Windows Vulnerability

Microsoft's efforts to crack down on researchers who release undisclosed bugs have been met with resistance from Nightmare Eclipse, a security researcher who has released a new Windows vulnerability called ShieldBreak. This bug targets Windows Defender, the built-in anti-malware engine that comes pre-installed with every copy of Windows.

The exploit, which allows an attacker to jump from a low-level user account to full system access, can be run as a downloadable Windows app and affects Windows 10, Windows 11, and Windows Server 2025. According to Nightmare Eclipse, ShieldBreak fully bypasses a previous fix that was meant to patch the issue.

This is not the first time Nightmare Eclipse has clashed with Microsoft over bug disclosures. The researcher has accused the company of mishandling previous reports, which led to several bugs being published publicly instead of being quietly patched. In response, Microsoft threatened legal action against researchers who go public with zero-days outside its disclosure rules.

However, the security community pushed back hard, and Microsoft eventually softened its stance on social media. For now, the company says it's 'aware of the reported vulnerability and is actively investigating.'