Microsoft closes book on Nightmare Eclipse's RoguePlanet zero-day

Microsoft has quietly fixed the "RoguePlanet" zero-day (CVE-2026-50656) in Microsoft Defender after researcher Nightmare Eclipse published technical details and proof-of-concept exploit code; the flaw exploited a race condition that could spawn a SYSTEM-level command prompt, the patch was delivered via an update to the Microsoft Malware Protection Engine, and Microsoft has not publicly confirmed any in-the-wild exploitation beyond the demonstrations.