Microsoft's patch for a Windows Defender 0-day may have created a new attack path

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Facepalm: Microsoft released an update for a recently unveiled zero-day vulnerability in Windows Defender, but the patch is apparently making things even worse. The researcher who first discovered the "RoguePlanet" flaw quickly found some potentially dangerous problems in the patch as well.

The feud between "NightmareEclipse" and Microsoft continues to hold unpleasant surprises for the Windows ecosystem. The disgruntled security researcher, who accused Redmond of hiding a pernicious backdoor in BitLocker's volume encryption, recently shared details about RoguePlanet, a new zero-day flaw that could be abused by cybercriminals to gain full administrative privileges on a patched Windows system.

NightmareEclipse also unveiled the proof-of-concept code required to exploit RoguePlanet, but Microsoft was quick to act. Just a week before this month's Patch Tuesday, the company released a patch for the flaw. Tracked as CVE-2026-50656, the vulnerability was apparently resolved through an update to Microsoft Defender's Malware Protection Engine (mpengine.dll).