Disgruntled security researcher just dropped another Windows zero-day, right on schedule

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Sounding off: NightmareEclipse did it again. The security researcher who's been on a crusade against Microsoft has published a new zero-day flaw affecting all supported Windows versions. Redmond threatened to sue, but the researcher is keeping his promise to disclose a new dangerous flaw after every month's Patch Tuesday.

NightmareEclipse and Microsoft keep clashing over zero-day vulnerabilities in Windows. The researcher, who pledged to give Redmond security hell, is back with ShieldBreak, a new flaw in Windows Defender that can be abused to gain complete, unfettered access to a Windows device and all its data.

The researcher described the latest flaw as a "funny bug" related to RoguePlanet, a previously disclosed vulnerability tracked as CVE-2026-50656. Microsoft released a fix for RoguePlanet in July, but NightmareEclipse now says the "official" patch fails to properly address the issue in Defender's end-point antivirus engine.