Open Cyber Threat Intelligence

CLOSEDQUORUM is a Windows-based malware implant that uses commercial large language models (LLMs) from DeepSeek, Qwen, Mistral, and Google Gemini as an autonomous command and control (C2) infrastructure. It delegates tactical decisions such as credential theft, process injection, and persistence to a panel of LLMs, which vote on the next action via a structured JSON schema. The malware targets user credentials and cryptocurrency wallets, exfiltrating stolen data via an operator-controlled Discord webhook using AES-256-GCM encryption and Base64 encoding. While the distributed version contains placeholder keys and is non-functional, development builds suggest a 'credentials-as-a-service' model where customized binaries are provided to operators.

A former Microsoft security researcher, Abdelhamid Naceri, publicly released a zero-day proof-of-concept tool called BigDiskBuster that blocks Microsoft Defender from installing platform and signature updates by consuming all available disk space. The tool monitors Defender's update paths and creates a large hidden temporary file to prevent update downloads, deleting it once the update attempt fails. This denial-of-service technique could leave Defender with outdated detection capabilities, increasing risk of undetected malware. No patch or CVE has been issued, and the tool reportedly works across all supported Windows versions.

A critical vulnerability in Bifrost, an open-source AI gateway, allows unauthenticated attackers to execute arbitrary commands on the gateway server via a single HTTP request. The flaw, tracked as CVE-2026-90898, affects all versions prior to 2.1.0 when management authentication is disabled by default. Attackers can exploit the /api/mcp/client endpoint to register a stdio-type MCP client, leading to immediate command execution as the gateway process user, potentially exposing stored API keys for LLM providers. A second related vulnerability, CVE-2026-86242, allows unauthenticated registration of a custom plugin from an HTTP URL, resulting in remote code execution or server-side request forgery depending on the build type.

Microsoft, in collaboration with multiple public and private partners, disrupted the EvilTokens phishing-as-a-service (PhaaS) platform, which leveraged AI to automate and scale business email compromise (BEC) attacks. The service abused OAuth 2.0 device authorization flows to gain persistent access to Microsoft accounts without stealing passwords, using social engineering to trick users into entering device codes on legitimate Microsoft login pages. EvilTokens offered AI-powered tools to analyze compromised inboxes, identify financial workflows, and draft convincing phishing emails, enabling even low-skill attackers to conduct sophisticated fraud. The operation led to the seizure of 50 websites, takedown of 150 domains, and the arrest of two individuals, with evidence linking the service to over 12,000 compromised inboxes across 10,000 organizations worldwide.

A malicious npm package named 'tw-pkgprobe-7731' was uploaded to the npm registry by a now-defunct account 'twdepprobe7731', masquerading as an authorized Twilio bug-bounty probe. The package targets Twilio developers by checking for specific environment conditions and, if met, exfiltrates environment variables, system configurations, and Twilio credentials such as ACCOUNT_SID and AUTH_TOKEN. Later versions attempted to inject malicious npm packages and perform OSINT gathering on Twilio-related infrastructure, though the final versions reverted to benign behavior, suggesting possible testing or evasion. The package violates Twilio's HackerOne security research guidelines and shows no obfuscation, indicating a low sophistication threat actor.

WordPress has patched a critical vulnerability, CVE-2026-87902, that allows unauthenticated attackers to exploit a path traversal flaw in the template loading mechanism, potentially leading to remote code execution on vulnerable servers. The vulnerability affects all WordPress versions from 4.7.0 to 7.1.1 and stems from insufficient sanitization of user-supplied input used to construct template file paths. Successful exploitation requires the active theme to have a top-level directory starting with 'page-' and depends on server-side PHP configuration (e.g., register_argc_argv enabled) for full code execution. While no active exploitation has been observed as of September 22, 2026, the flaw is rated with a CVSS score of 9.2 and affects a wide range of WordPress installations.

Check Point has released emergency hotfixes for a critical zero-day vulnerability, CVE-2026-93616, in its Security Management Server that allows unauthenticated attackers to perform path traversal and upload and execute arbitrary scripts. The vulnerability is actively exploited in the wild, with Check Point confirming attacks against a handful of customers. The affected products include Security Management Server, Multi-Domain Security Management Server, Log Server, Multi-Domain Log Server, and SmartEvent. CISA and FBI have previously warned software vendors about the persistence of such path traversal flaws, which remain a high-risk attack vector.

Cisco Talos discovered a new Windows malware named ClosedQuorum, which autonomously makes post-compromise attack decisions using multiple AI models including Google Gemini, DeepSeek, Qwen, and Mistral. The malware uses a voting system among the AI models to decide actions such as credential theft, code injection, persistence, and lateral movement, with DeepSeek breaking ties. Stolen data is exfiltrated via Discord webhooks. While the sample analyzed contains placeholder credentials and no active lateral movement capability, it represents an early example of fully automated, AI-driven attack chains with no human operator involvement.

The ShinyHunters extortion gang claims to have breached FBI systems using an unpatched zero-day vulnerability in Oracle PeopleSoft, enabling remote code execution and lateral movement into FBI-managed AWS GovCloud infrastructure. They allege exfiltration of 2–3TB of sensitive data, including personally identifiable and health-related information of current and former FBI employees and job applicants. ShinyHunters defaced the FBI Jobs website (apply.fbijobs.gov) with their branding and claim to be exploiting the same vulnerability against Fortune 500 companies. The group stated the attack was retaliation for an FBI FLASH report published in May 2026, and they have not ruled out releasing the stolen data.

A vulnerability in SharePoint Server, tracked as CVE-2026-65660, initially misclassified by Microsoft as a spoofing flaw, actually enables authenticated remote code execution. The flaw affects SharePoint Server 2016, 2019, and Subscription Edition, and stems from improper handling of double quotes in web-part markup within the ToolPane component, allowing arbitrary .NET class registration and subsequent code execution via XamlServices.Parse() deserialization. Researcher Dinh Ho Anh Khoa demonstrated the exploit and noted it could be chained with a previously patched authentication bypass to achieve pre-authentication RCE on anonymously accessible servers. Although no in-the-wild exploitation has been reported, the full exploit is public, and the patch was released in Microsoft's August 11 updates.