zero-day Archives

Tech Optimizer

September 23, 2026

BigDiskBuster PoC Blocks Windows Defender Updates

A new tool named BigDiskBuster has been released on GitHub, which disrupts Microsoft Defender Antivirus by preventing it from installing updates. It does this by consuming available disk space during the update process, causing Defender to remain on its current version and unable to receive new platform or signature updates. BigDiskBuster operates as a local denial-of-service technique and requires prior access to the target machine to execute. The tool was created by researcher Abdelhamid Naceri, known as Nightmare Eclipse, who has previously worked on similar projects. As of now, there is no CVE identifier, patch, or advisory from Microsoft regarding this issue.

Winsage

September 23, 2026

New Windows Defender zero-day blocks Microsoft antivirus updates

Security researcher Abdelhamid Naceri, known as Nightmare Eclipse, released a zero-day exploit called BigDiskBuster that targets Microsoft Defender, preventing antivirus updates and leaving systems vulnerable. BigDiskBuster operates across all supported Windows versions and must run in the background to block updates. Naceri has previously released a similar exploit called UnDefend and has a history of releasing multiple zero-day exploits since April 2026 amid a dispute with Microsoft. Two weeks before BigDiskBuster, he introduced another exploit named ShieldCrash, which grants SYSTEM access and circumvents a patched flaw. Naceri's recent exploits include tools like LegacyHive, BlueHammer, RedSun, YellowKey, GreenPlasma, and MiniPlasma, all targeting Microsoft Defender and other Windows components. Microsoft has warned of potential legal action against malicious activities but has not commented on BigDiskBuster.

Winsage

September 21, 2026

Do This If You Want Another Year of Windows 10 Security Updates

Microsoft has extended its security update support for Windows 10 until October 12, 2027, through the Extended Security Updates (ESU) program. This extension allows users to maintain essential protection against threats despite the official end of support last year. The ESU program will continue for existing participants without further action required, while new users can enroll until the program concludes next year. To qualify, devices must be running Windows 10 version 22H2 and have the latest updates installed. Enrollment options include purchasing coverage or redeeming Microsoft Rewards points. The program focuses solely on security, providing critical monthly updates without new features.

Tech Optimizer

September 15, 2026

Best Free Antivirus: 11 Steps, 18/18 Score [2026]

Microsoft Defender scored 17.5 out of 18 in the June 2026 evaluations by AV-Test, while Avast Free Antivirus and AVG AntiVirus Free both achieved a perfect score of 18 out of 18. Avira Internet Security scored 16.5. The evaluations assessed 16 consumer antivirus products based on protection, performance, and usability. Microsoft Defender is built into Windows 11 and is free, while Avast and AVG are true free offerings. AV-Test uses a scoring system where each category is scored out of 6.0, leading to a maximum total of 18.0. Users should ensure they have the latest versions of antivirus products and only run one real-time antivirus engine at a time. Common pitfalls include running two real-time engines and downloading from unofficial sources. For low-risk users, Microsoft Defender is sufficient, while those seeking higher protection may consider Avast or AVG.

Winsage

September 15, 2026

China-Linked Hackers Exploit Chrome-Windows Zero-Day Chain to Deploy GRIMWEDGE

A spear-phishing campaign linked to the Chinese threat actor UTA0560 targeted various NGOs on September 1, 2026, exploiting recently patched vulnerabilities in Google Chrome and Microsoft Windows. The campaign utilized a malicious JavaScript backdoor called GRIMWEDGE, which was deployed through a multi-stage exploit chain that involved three vulnerabilities: CVE-2026-85046, CVE-2026-87491, and CVE-2026-85880. The attack began with spear-phishing emails that led recipients to a vulnerable U.S.-based university website, allowing attackers to redirect users to their infrastructure. The exploit chain enabled arbitrary code execution and facilitated the deployment of GRIMWEDGE, which is capable of host reconnaissance, file and process management, command execution, and payload delivery. The initial payload was an executable named "msgbox.exe," which extracted a legitimate Windows binary and a malicious DLL called "wsc.dll." This DLL initiated a sideloading chain and contacted a command-and-control server for further instructions. GRIMWEDGE allows for several commands, including system reconnaissance, directory listing, file deletion, and command execution in a hidden window. It lacks built-in persistence or lateral movement mechanisms but provides a foothold for further exploitation. Concurrently, another Chinese threat actor, JungleBamboo (APT31), used the same exploit chain to deploy a loader named SUPERSTOMP, which installs a credential-stealing Chrome extension called LONGTALE. The simultaneous use of the exploit chain by multiple actors suggests potential sharing or sale of the exploit, raising concerns about patch-gap vulnerabilities that pose risks for exploitation campaigns.

AppWizard

September 15, 2026

Active Exploitation Alert: Threat Actors Abuse Anthropic Claude AI to Extract Secrets from 1.8M Android Apps in Major Credential Theft Campaign

Between December 2025 and August 2026, a coalition of advanced threat actors exploited the Claude AI model by extracting sensitive information from approximately 1.8 million Android applications. The operation involved groups such as ShinyHunters, Midnight Blizzard (APT29/Nobelium), and the Chinese-speaking entity GTG-10007. They automated the mass download, decompilation, and analysis of Android APKs for hardcoded credentials, API keys, and authentication tokens, leading to extensive credential theft and breaches across various sectors. The attack utilized a distributed pipeline on ten AWS EC2 instances to download APKs, which were then scanned using TruffleHog. Verified secrets were organized and routed in real-time to a private Telegram group for operational deployment. Over 2,100 Azure AD authentication tokens were extracted from more than 40 Microsoft tenants within 34 hours. The operation also included a carding component where stolen payment card data was sold. The tactics employed aligned with several MITRE ATT&CK techniques, including file discovery, unsecured credentials, valid accounts, phishing, and exploitation of remote services. ShinyHunters gained administrative control over targeted environments rapidly, leading to bulk data theft affecting over 200 organizations. Midnight Blizzard automated malware creation and phishing campaigns, targeting government and defense entities. GTG-10007 used Claude for coordinated offensive operations, discovering zero-day vulnerabilities and delivering exploits. Initially, the campaign targeted a broad range of Android APKs but later focused on organizations with valuable credentials across various sectors, including government, technology, and healthcare. Compromises were confirmed in Southeast Asia, Europe, and the Middle East. Organizations are advised to audit Android applications for hardcoded secrets, monitor API key usage, and implement robust security practices to mitigate risks.

Winsage

September 10, 2026

Microsoft patches 966 vulnerabilities: Two Windows zero-days actively exploited

On September 8, 2026, Microsoft released 966 security updates, the largest Patch Tuesday to date, addressing various vulnerabilities. Among these, 105 were classified as critical, including two zero-day vulnerabilities: CVE-2026-81963 and CVE-2026-85880. Both allow authorized local attackers to escalate privileges to SYSTEM level. CVE-2026-81963 is related to the Windows Update Stack, while CVE-2026-85880 involves a heap-based buffer overflow in the Windows Advanced Local Procedure Call (ALPC). The updates included 438 vulnerabilities related to privilege escalation, 258 concerning remote code execution, and 173 involving information disclosures. Users are advised to prioritize the installation of these updates due to the potential exploitation of the two critical vulnerabilities.

Winsage

September 9, 2026

Latest Windows 11 update restores your taskbar control, patches 995 security flaws

Microsoft's September Patch Tuesday update for Windows 11 introduces several enhancements, including the ability to reposition the taskbar to the top, left, or right sides of the screen. Users can adjust the taskbar's alignment, height, and icon size, though the auto-hide feature is limited to the bottom position. The Start menu now allows users to select between Small and Large sizes, with the Recommended section rebranded as Recent, and options to hide their name and profile picture. The Search window has been streamlined to focus on suggested or recent searches. The update addresses 995 security vulnerabilities, including 121 critical vulnerabilities and two zero-day flaws (CVE-2026-81963 and CVE-2026-85880), which could allow attackers to gain system-level privileges.

Winsage

September 9, 2026

Microsoft Patches Record 974 Flaws, Including Two Exploited Windows Zero-Days

Microsoft addressed 974 vulnerabilities in its software suite during its recent Patch Tuesday, marking a record high. The breakdown includes 723 flaws in Windows, 111 in Office, 62 in SQL, and 22 in Developer Tools, with over 110 rated as critical. Two actively exploited vulnerabilities are CVE-2026-85880 and CVE-2026-81963, both allowing local privilege elevation. Other notable vulnerabilities include CVE-2026-55007 (8.1), CVE-2026-80097 (8.6), CVE-2026-69465 (8.8), and several with CVSS scores of 9.6 and above. Microsoft has patched a total of 2,760 security flaws this year, reflecting a trend of increasing vulnerability discoveries. Despite the extensive patching, no significant spike in active exploits has been observed.

Tech Optimizer

September 8, 2026

Microsoft Confirms False “Defender Antivirus Turned Off” Alerts Spreading Across Windows Devices

Microsoft has acknowledged a software bug causing persistent Windows Security pop-ups that incorrectly indicate antivirus protection is disabled. These notifications began appearing after the latest Microsoft Defender Antivirus updates, but the antivirus is functioning correctly. The issue affects various versions of Windows and Windows Server with the latest Defender updates. Microsoft has committed to resolving the issue in a future update, though no timeline has been provided. Users are advised to verify the status of their antivirus through the Windows Security app and disregard the notifications until a fix is released.