A researcher known as “Chaotic Eclipse” has revealed a new zero-day vulnerability in Microsoft Defender, called “RedSun,” which allows local privilege escalation to SYSTEM privileges on Windows 10, Windows 11, and Windows Server when Microsoft Defender is enabled. The exploit has been confirmed to function correctly, and some antivirus vendors have begun detecting it. This follows another vulnerability disclosure by the same researcher, named BlueHammer, which also allows local attackers to elevate permissions. Chaotic Eclipse expressed dissatisfaction with Microsoft’s handling of vulnerability disclosures, claiming they were threatened and experienced frustration with the company’s response. A Microsoft spokesperson stated the company is committed to investigating reported security issues and supports coordinated vulnerability disclosure.