Microsoft Defender
New Windows Defender zero-day blocks Microsoft antivirus updates
Over the weekend, security researcher Abdelhamid Naceri (also known as Nightmare Eclipse) released another Microsoft Defender zero-day exploit that blocks antivirus updates. Naceri named it BigDiskBuster and said it is similar to another Defender zero-day known as UnDefend, which he released in April and that allowed standard users to block definition updates. The security researcher added […]
Microsoft fixes bug behind ‘Defender Antivirus is turned off’ alerts
Microsoft has resolved a known issue that causes incorrect alerts warning that Defender Antivirus was turned off after installing recent updates. In a Windows release health dashboard update on Thursday, Microsoft said the issue was fixed in the Microsoft Defender Antivirus update (version 4.18.26080.4) released on September 17. The company acknowledged the bug in late […]
New Microsoft Defender ‘ShieldCrash’ zero-day grants SYSTEM access
An anonymous security researcher known as Nightmare Eclipse has released a new Microsoft Defender zero-day exploit named “ShieldCrash” right after Microsoft rolled out its September 2026 Patch Tuesday security updates. ShieldCrash is described as a bypass for the ShieldBreak Defender privilege escalation flaw patched on Thursday, which itself bypassed RoguePlanet, another Defender flaw disclosed in June and patched by Microsoft […]
Microsoft Defender flags legitimate Google search links as malicious
Microsoft is investigating an issue causing the Defender for Office 365 security software to mistakenly flag legitimate Google search links as malicious. The company first acknowledged the incident (tracked under MO1465962) at 10:30 AM UTC and says affected users are seeing “Opening this website might not be safe” warnings when trying to open the blocked hyperlinks. […]
Microsoft asks users to ignore ‘Antivirus is turned off’ errors
Microsoft asked customers this week to ignore incorrect alerts that Defender Antivirus has been turned off after installing the latest Defender updates. Although this issue has been affecting users in the Release Preview Channel of the Windows Insider program since June, it appears Microsoft didn’t notice it until now. The erroneous alerts appear on affected systems in the Windows […]
Microsoft fixes known issue causing Windows Defender crashes
Microsoft has resolved a bug that caused Windows Defender to crash after a recent security update, resulting in 0xc0000005 access violation errors on some affected systems. Microsoft Defender is a security software designed to provide real-time protection against malware, viruses, ransomware, and spyware on Windows, macOS, Linux, Android, and iOS devices. According to reports on social media and Microsoft’s support site, users […]
Microsoft working on Defender patch for ShieldBreak zero-day
On Friday, Microsoft confirmed it has begun working on a security patch for a Defender zero-day vulnerability named “ShieldBreak.” A security researcher who uses the “Nightmare Eclipse” handle disclosed this privilege escalation vulnerability after Microsoft released the August 2026 Patch Tuesday security updates. ”Microsoft is aware of the reported vulnerability and is actively investigating the […]
New Microsoft Defender ‘ShieldBreak’ zero-day grants SYSTEM privileges
A security researcher known as Nightmare Eclipse has released a new Microsoft Defender zero-day exploit named “ShieldBreak” after Microsoft released the August 2026 Patch Tuesday security updates. The new vulnerability is described as a bypass for RoguePlanet, another Defender privilege escalation flaw disclosed in June and patched by Microsoft one month later. However, cybersecurity expert Kevin […]
Microsoft patches RoguePlanet Defender zero-day vulnerability
Microsoft has released a security patch to address a Defender zero-day vulnerability known as “RoguePlanet,” disclosed after the June 2026 Patch Tuesday. The flaw (tracked as CVE-2026-50656) was disclosed by a security researcher using the “Nightmare Eclipse” handle as part of an ongoing dispute with Microsoft over the company’s bug bounty and vulnerability disclosure practices. They […]
Microsoft working on Defender patch for RoguePlanet zero-day
Microsoft confirmed that it’s working on a security patch for a Defender zero-day vulnerability named “RoguePlanet,” disclosed one week ago. The security researcher who published a RoguePlanet exploit during the June 2026 Patch Tuesday (known as Nightmare Eclipse) said it affects fully patched Windows 10 and Windows 11 devices and allows attackers to spawn command prompts with […]