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Researcher drops two more Microsoft Defender zero-days, all three now exploited in the wild

Feeds2.Feedburner •Zeljka Zorz • April 17, 2026

The security researcher who earlier this month published a proof-of-concept (PoC) exploit for a zero-day privilege escalation vulnerability in Microsoft Defender is back with two more. The first, dubbed “RedSun,” is another privilege escalation flaw in the same platform. The second, “UnDefend,” allows a standard user to block Microsoft Defender from receiving signature updates or disable it entirely (if Microsoft pushes a major Defender update). And, according to Huntress researchers, all three exploitation techniques have … More →

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This article is one source in a clustered incident — the cluster page carries the summary, timeline and every other outlet covering it.

BlueHammer Zero-Day Exploit Released, Exposing Windows Users to Privilege Escalation A security researcher, known as Chaotic Eclipse, has publicly released exploit code for a zero-day vulnerability in Windows, dubbed BlueHammer, allowing local privilege escalation to SYSTEM or elevated administrator privileges. The exploit targets a flaw in the Windows Defender update mechanism and has no available patch, leaving potentially over 1 billion Windows users vulnerable. The researcher expressed frustration with Microsoft's Security Response Center (MSRC) regarding their handling of the vulnerability disclosure process, leading to the public release of the exploit. Will Dormann, a principal vulnerability analyst, confirmed the exploit's functionality, noting that it is not entirely reliable and primarily affects local user accounts. The exploit code is available on GitHub, with significant interest from both security researchers and potential attackers. Microsoft has not yet issued a statement regarding a patch or a timeline for addressing the vulnerability. The exploit's release has raised concerns about the implications for cybersecurity, as attackers could leverage this flaw for malicious purposes. 130 sources 67

Extracted Entities

Researcher drops two more Microsoft Defender zero-days, all three now exploited in the wild

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Extracted Entities

Attack Types (1)

MITRE ATT&CK (1)

Platforms (1)

Vulnerabilities (2)