Microsoft has come out strongly against uncoordinated zero-day disclosures after researcher Chaotic Eclipse (also Nightmare-Eclipse) dropped technical details of six Windows zero-days over the past month, citing a breakdown in Microsoft's disclosure process. The CVEs include BlueHammer (CVE-2026-33825), RedSun (CVE-2026-41091), UnDefend (CVE-2026-45498), YellowKey (CVE-2026-45585), GreenPlasma, and MiniPlasma; BlueHammer, RedSun, and UnDefend are now under active exploitation. GitHub removed the researcher's account; a GitLab re-upload account was also blocked. Microsoft is urging coordinated vulnerability disclosure but the researcher publicly disputes Microsoft's responsiveness, citing months of waiting for fixes. The incident highlights ongoing friction between solo researchers and large vendor PSIRTs.
Microsoft has warned of an active cryptojacking campaign that surfaces malicious download sites through AI chatbot recommendations, extending SEO poisoning beyond conventional search. Attackers impersonate legitimate system utilities - CrystalDiskInfo, HWMonitor, Display Driver Uninstaller, FurMark, K-Lite Codec Pack, PDFgear - to target users with high-performance GPUs, prioritizing mining yield per host over mass infection. Beyond mining, the operators deploy ScreenConnect for persistent remote access enabling data theft, lateral movement, or ransomware. Victims who ask LLM-based tools for software-download recommendations are served links to attacker domains on subdomains of gleeze[.]com, hosted via Dynu dynamic DNS. Microsoft says it has detected and blocked the activity.
Microsoft has rolled out a preview of automatic device isolation in Microsoft Defender for Endpoint as part of its automatic attack disruption feature. When Defender detects a compromised endpoint, it now disconnects the device from the network without operator action, while preserving the Defender management channel so the host can still be monitored, investigated, and released. Security teams can release a device from containment after triage via 'Release from isolation' on the Device inventory or device page. The feature works only on onboarded end-user workstations. It joins earlier preview controls for blocking traffic to unmanaged endpoints and isolating compromised user accounts.
Microsoft has released an out-of-band patch for CVE-2026-45659, a remote code execution vulnerability in Microsoft SharePoint Server. The flaw is a deserialization issue and was reported privately by a researcher named MEOW; Microsoft says it is not currently aware of active exploitation but rates it 'less likely to be exploited.' Updates are available for SharePoint Server Subscription Edition, SharePoint Server 2019, and SharePoint Enterprise Server 2016. Last month's CVE-2026-32201 spoofing flaw was actively exploited and machine-key-theft attacks against SharePoint were widespread in 2025, so admins should treat this patch as priority despite the lower-likelihood rating.
Microsoft has rolled out fixes for two Defender vulnerabilities that have been exploited in zero-day attacks. CVE-2026-41091 is a link-following local privilege escalation in Microsoft Malware Protection Engine 1.1.26030.3008 and earlier that lets attackers gain SYSTEM. CVE-2026-45498 affects Defender Antimalware Platform 4.18.26030.3011 and earlier and triggers denial-of-service. Updates land automatically in Malware Protection Engine 1.1.26040.8 and Antimalware Platform 4.18.26040.7. CISA has added both to its KEV catalog and ordered FCEB agencies to patch within two weeks, by June 3. The same KEV update also added five legacy 2008-2010 Internet Explorer, DirectX, Acrobat, and Windows bugs that CISA suggests are seeing fresh exploitation.
Microsoft has assigned CVE-2026-45585 and shipped mitigation guidance for YellowKey, a Windows BitLocker bypass that anonymous researcher 'Nightmare Eclipse' disclosed last week with a working PoC. The attack places crafted FsTx files on a USB drive or EFI partition, reboots into WinRE, and holds CTRL during boot to drop into a shell with full access to BitLocker-protected drives. Microsoft says no patch is available yet. Mitigations include removing the autofstx.exe entry from Session Manager's BootExecute and reconfiguring BitLocker to require TPM+PIN at startup. Nightmare Eclipse is the same researcher who recently dropped BlueHammer, RedSun, GreenPlasma, UnDefend, and MiniPlasma.
Microsoft's Digital Crimes Unit, supported by law enforcement, has disrupted Fox Tempest, a 'malware-signing-as-a-service' offering that abused Azure Artifact Signing (formerly Trusted Signing) to issue legitimate Microsoft-signed certificates for malware. Operators created more than 1,000 certificates and hundreds of Azure tenants using stolen US and Canadian identities, all valid for 72 hours to reduce takedown risk. Microsoft has revoked the certificates, seized the signspace[.]cloud domain, and taken hundreds of supporting VMs offline. The service signed Oyster, Lumma Stealer, Vidar, and ransomware payloads for Rhysida, Akira, INC, Qilin, and BlackByte, used by groups including Vanilla Tempest and Storm-0501.
A researcher who goes by Chaotic Eclipse has dropped working proof-of-concept code on GitHub for a Windows local privilege escalation that gives SYSTEM access on fully patched Windows 11 Pro and Windows Server 2025. The bug lives in the Cloud Filter driver cldflt.sys and is, the researcher says, the same flaw Google Project Zero reported to Microsoft as CVE-2020-17103 in 2020, which Microsoft said it fixed in December 2020. The original Google PoC works unmodified. May 2026 Patch Tuesday updates do not stop it. The same researcher has dropped several other Windows zero-days in recent weeks, all of which were quickly seen in real attacks.
Microsoft has flipped its position on Edge keeping saved passwords decrypted in memory the moment the browser launches. After originally telling the researcher who reported it that the behavior was 'by design' and not a security issue, Microsoft now says future Edge builds will stop loading the password store into memory at startup. The fix is already live in the Canary channel and will reach Stable, Beta, Dev, and Extended Stable in build 148. The original disclosure came with a working tool that lets an administrator on a shared Windows machine dump other users' Edge passwords by reading process memory.
Microsoft has refused to issue a CVE for what an outside researcher and the CERT Coordination Center both describe as a privilege escalation in Azure Backup for Azure Kubernetes Service. The flaw lets a user holding only the low-privileged 'Backup Contributor' Azure role gain cluster-admin on AKS clusters, which Microsoft dismissed by saying the attacker 'already held administrator access.' CERT/CC validated the bug and tracked it as VU#284781. The researcher says Microsoft also tried to get MITRE to reject the submission as 'AI-generated content,' then quietly added new permission checks, suggesting a silent patch even as Microsoft says 'no product changes were made.'
TrustStrike Labs