Researcher NightmareEclipse Publishes Windows Zero-Day ‘ShieldBreak’ Bypassing Defender Patches

On August 13, 2026, security researcher NightmareEclipse disclosed a new Windows zero-day vulnerability, dubbed ‘ShieldBreak,’ targeting Microsoft Defender. According to the report, the flaw can completely bypass previous security patches and grant full, unrestricted device access on all supported Windows versions. The disclosure was made as part of the researcher’s planned public release. Microsoft has not yet issued a response. Users are advised to monitor updates from Microsoft.