A threat campaign tracked as Key Eater is exploiting stolen Microsoft Entra ID application credentials to breach Microsoft 365 and Azure environments across 27 organizations since November 1, 2026. Attackers have successfully authenticated into over 33 compromised app registrations across approximately 18 organizations, accessing 2,279 mailbox items and downloading 81 files. Victims span government, energy, agriculture, transportation, engineering, legal, education, and nonprofit sectors. Attackers are also leveraging MSP integrations to amplify exposure across customer tenants.
Threat actors, including a China-linked group tracked as STORM-0940/UNC7228, are exploiting the open-source ARTEX AI agent framework to automate attacks against Microsoft 365 tenants using stolen ConnectWise credentials. ARTEX performs reconnaissance, credential theft through Kerberoasting, and lateral movement via Active Directory manipulation at machine speed—achieving deep system access in under 15 minutes in some cases. The framework chains standard Windows administrative techniques but executes them at scale with minimal human intervention, trading stealth for speed and leaving detectable audit logs.
CVE-2026-111497, a critical Brotli decoder vulnerability (CVSS 9.8), is being actively exploited to achieve remote code execution or information disclosure. Microsoft .NET 8, 9, 10, and 11—foundational components used by Microsoft 365 services—are affected. Exploitation requires an application to decompress attacker-controlled Brotli-compressed data. Public proof-of-concept code is available. Immediate patching is required.
Threat actors are abusing Microsoft Teams' external chat feature to conduct large-scale social engineering campaigns against organizations. Arctic Wolf documented over 400 incidents where attackers flood employee inboxes with spam, then contact victims posing as IT support using newly created Teams identities, leading to remote access tool installation and code execution in under 15 minutes. The campaign, observed by multiple ransomware groups including Black Basta and Chaos, relies on abuse of default-enabled Teams federation rather than a technical vulnerability.
CVE-2026-80097, a high-severity elevation-of-privilege vulnerability in Microsoft Authenticator for Android (CVSS 8.6), allows malicious applications without any Android permissions to impersonate trusted Microsoft apps and steal authentication tokens. The flaw stems from improper validation in the exported AccountChooserActivity, enabling attackers to extract access tokens, refresh tokens, and ID tokens that can be reused to gain unauthorized access to Microsoft 365 resources including Teams, SharePoint, OneDrive, and Exchange. Microsoft released a fix in version 6.2606.4246.
Microsoft's October 2026 Patch Tuesday addressed 1,413 CVEs including critical flaws in Microsoft 365 components. CVE-2026-70242 (Outlook Reading Pane RCE, CVSS 9.8) allows remote code execution via email preview without user interaction; CVE-2026-102866 (SharePoint EoP, CVSS 8.1) enables elevation of privilege. Additionally, CVE-2026-96951 (Windows Shell MOTW bypass, CVSS 8.8) is under active exploitation, allowing crafted files to circumvent Office Protected View and macro blocking.
A China-aligned threat group (Storm-0940) conducted a large-scale password spray and supply-chain attack against Microsoft 365 tenants in October 2026. Attackers exploited a compromised ConnectWise Cloud Backup application—trusted by thousands of organizations—to attempt sign-ins to over 2,250 tenants at 2,900 attempts per minute using an open-source AI agent framework (ARTEX). Microsoft reports the group achieved privileged access to multiple organizations in less than 3 hours. The campaign demonstrates how threat actors are automating offensive operations with agentic AI to scale attacks exponentially.
Huntress researchers disclosed a widespread token-spraying campaign targeting Microsoft 365 accounts globally. Between July and September 2026, attackers conducted ~200,000 login attempts against 79 organizations, achieving 497 successful sign-ins. Attackers used phishing, adversary-in-the-middle (AiTM) techniques, and stolen session tokens to bypass MFA, then modified Entra settings, created hidden inbox rules, and registered malicious devices to maintain persistence. The campaign prepared infrastructure for business email compromise attacks.
ConnectWise shut down its Cloud Backup service after attackers accessed application identities and compromised at least 162–173 Microsoft 365 tenants. The malicious activity began October 15, 2026, involving unauthorized authentication and privilege escalation (e.g., Exchange Administrator role assignment). ConnectWise's cloud backup solutions use Microsoft Entra ID service principals to access customer tenants; the compromise exposed this trust relationship. Microsoft confirmed unauthorized authentication attempts; ConnectWise states backup archives appear uncompromised but investigation ongoing.
Microsoft released patches on October 16, 2026 for over 30 vulnerabilities in the Office suite, including two dozen high-severity remote code execution flaws. Multiple RCE bugs can be exploited via Preview Pane, with some requiring specially crafted files. The update also fixes information disclosure bugs and security bypass issues.
CVE-2026-70242, a critical heap-based buffer overflow in Microsoft Office Outlook, allows remote code execution without user interaction or authentication (CVSS 9.8). The vulnerability affects Microsoft 365 Apps, Office 2024, and Office 2021. Microsoft published the CVE on October 13, 2026, and reference guidance is available on MSRC. No active exploitation has been confirmed at the time of disclosure.
Microsoft released its October 2026 Patch Tuesday on October 13, addressing a record-breaking 1,411 vulnerabilities including 70 critical flaws. The update includes one actively exploited zero-day (CVE-2026-96951, Windows Shell security feature bypass) and two publicly disclosed zero-days (CVE-2026-108398 in .NET Framework, CVE-2026-92707 in MessagePack-CSharp). Notable patches address remote code execution flaws in SQL Server, SharePoint elevation-of-privilege vulnerabilities, and Office component weaknesses. This represents the largest security update in Microsoft history.
CVE-2026-102855, a high-severity heap-based buffer overflow in Microsoft Office Visio (Microsoft 365 Apps for Enterprise, CVSS 8.8), allows remote code execution over a network. The vulnerability affects Microsoft 365 Apps for Enterprise version 16.0.1 and later, Microsoft Office LTSC 2021, and Microsoft Office LTSC 2024. Microsoft released patch guidance on October 13, 2026.
FBI and international agencies released a joint advisory on October 8, 2026, warning of ongoing Chinese government-linked attacks exploiting Microsoft Exchange and Outlook infrastructure. Threat actors use EBurst for password spraying against Outlook Web Access and Exchange Web Services, and a tool called office-cli to automate access to Microsoft Outlook 365 mailboxes for email exfiltration. The campaign also targets Active Directory for credential theft and uses VPN clients for persistence across diverse sectors including critical infrastructure.
Nikkei Inc. disclosed on October 5, 2026 that threat actors compromised two email accounts: a Microsoft 365 account used to send approximately 9,000 phishing emails to internal and external contacts on September 30, and a Google Workspace account accessed since late July exposing names and email addresses of 1,646 employees and business partners. No specific threat actor has been attributed, and no malware or advanced persistence was identified. Remediation included password resets and regulatory notification to Japan's Personal Information Protection Commission.
China-based Warlock ransomware group, tracked as Longlegs and Storm-2603, has been actively exploiting SharePoint vulnerabilities since July 2025 against critical infrastructure, government, and education entities. Symantec reports the group continues to target SharePoint servers as part of ongoing ransomware operations.
Microsoft published CVE-2026-96940, a high-severity elevation of privilege vulnerability in Microsoft Exchange Server 2016, 2019, and Subscription Edition. An authenticated attacker can exploit weak authorization to access other users' mailboxes within the same organization without user interaction. CVSS score 8.8. Microsoft rates exploitation as "More Likely" and has released patches (KB5129958, KB5129957, KB5129956, KB5129955).
Threat actors tracked as UNK_CondorFiltration conducted a password-spraying campaign against 5,700+ Microsoft 365 accounts across 28 tenants using the TeamFiltration framework, successfully compromising seven unmanaged service accounts at Chilean retail and financial organizations between July 21 and August 16, 2026. Attackers leveraged forgotten service accounts lacking MFA and predictable default credentials to gain access to Teams, OneDrive, SharePoint, and Azure Portal resources. All seven confirmed compromises were dormant functional accounts used for business processes, with no evidence of ordinary employee account takeover.
A 16-year-old security researcher (Faav) discovered a JWT signature validation bypass in Microsoft's internal Titan analytics service on August 25, 2026. The flaw allowed forged administrator access and arbitrary SQL queries without authentication, potentially exposing metadata from 17.3 trillion database rows across 24 analytics configurations and 9 ClickHouse databases. The vulnerability was reported to MSRC on September 5, patched server-side on September 9, and publicly disclosed September 26. Microsoft awarded a $5,000 bounty; no evidence of malicious exploitation was found.
Cybercriminals are conducting active social engineering attacks via Microsoft Teams, impersonating IT help desk staff to trick employees into installing malware (SynkLoader), granting remote access, or revealing Windows passwords via fake lock screens. Attackers leverage Microsoft 365 tenants they control to contact users through Teams external chat. The campaign exploits default cross-tenant communication settings and employee trust in internal support channels; no software vulnerability is involved. Organizations are advised to restrict Teams external access to trusted domains only and train employees to verify unexpected support requests.
CVE-2026-100208 is a high-severity (CVSS 7.5) integer overflow vulnerability in Microsoft Office Outlook that allows unauthorized attackers to execute code remotely via network-based attack. The flaw requires user interaction and was publicly disclosed on September 25, 2026. Microsoft has issued guidance; no public exploit code has been confirmed, but organizations should prioritize patching to prevent exploitation.
CVE-2026-85889, a CVSS 10.0 missing-authentication vulnerability in Azure AI Foundry, allows unauthenticated remote attackers to escalate privileges and take over AI workloads via the control plane. Microsoft patched the flaw server-side on September 18, 2026, requiring no customer action but leaving deployments invisible to outside auditing. The vulnerability was part of a 12-CVE cluster affecting Azure and Microsoft 365 services, with seven flaws reaching maximum CVSS scores, affecting over 100,000 enterprise customers.
CVE-2026-81951 is a critical heap-based buffer overflow in Microsoft Excel affecting Microsoft 365 Apps, Office 2016, 2019, LTSC 2021/2024, and Office for Mac. The vulnerability requires user interaction (opening a malicious Office file) but enables local code execution with high impact to confidentiality, integrity, and availability. Microsoft released fixes on September 24, 2026. Exploitation has not been observed in the wild, but the breadth of affected installations makes rapid patching a priority.
CVE-2026-65660, a SharePoint Server vulnerability affecting 2016, 2019, and Subscription Edition, was initially misclassified by Microsoft as a spoofing flaw but actually enables authenticated remote code execution via arbitrary .NET class loading and deserialization. Microsoft patched the flaw on August 11, 2026; no in-the-wild exploitation has been reported, though full technical details and working exploit code were published on September 22, 2026.
A proof-of-concept denial-of-service technique named BigDiskBuster, published on GitHub on September 21, 2026, can prevent Windows Defender from completing platform and security intelligence signature updates. The technique exploits unspecified Windows behavior to block Defender's update mechanisms, potentially leaving endpoints with outdated malware detections and reduced protection against new threats. No official CVE has been assigned, and Microsoft has not yet acknowledged the issue. The proof-of-concept code is written in C++ and has garnered significant GitHub interest (130+ stars, 20+ forks).
Microsoft's September 2026 Patch Tuesday addressed a record 966 vulnerabilities across Windows, Office, and Azure. Two vulnerabilities were already being actively exploited in the wild before patches shipped. Approximately 20 flaws are classified as wormable, with critical impact on DHCP, MSMQ, NFS, and VPN (SSTP) services; a particularly dangerous unauthenticated remote code execution vulnerability in Windows DNS Server was compared to the 2020 SigRed vulnerability. Organizations should prioritize patches for internet-facing DNS servers and network infrastructure components immediately.
Plugin4Shell is a zero-click remote code execution vulnerability affecting GitHub Copilot and other AI coding agents. The flaw exploits Git reference name ambiguity to allow attackers to replace SHA-pinned plugins with malicious code without user interaction. Microsoft had not released a patch for Copilot at disclosure; organizations should update supported agents and audit installed plugins.
CVE-2026-85885 is a command injection vulnerability (CWE-77) in Microsoft 365 Copilot that allows authorized attackers to elevate privileges remotely with no user interaction required. The CVSS 3.1 score is 9.9 (critical), with complete impact on confidentiality, integrity, and availability. Microsoft has released an official fix managed server-side for the cloud service.
CVE-2026-78501 is a command injection vulnerability (CWE-77) in Microsoft 365 Copilot's Business Chat that allows unauthorized attackers to disclose sensitive information over a network with high confidentiality impact. The vulnerability requires user interaction and has a CVSS 3.1 score of 7.4. Microsoft has released an official fix and manages remediation server-side for this cloud service.
NightEagle (APT-Q-95) has deployed GhostContainer backdoor on Microsoft Exchange servers and abused Microsoft Dev Tunnels to establish persistent access and hide RDP connections within corporate networks. The threat group targets Russian and Asian organizations with compromised VPN credentials, Exchange server exploitation, and Active Directory attacks for lateral movement.