Loading story…
Security researchers at LayerX disclosed a zero-click remote code execution (RCE) issue in Anthropic Claude Desktop Extensions that can be triggered by a malicious Google Calendar event, enabling silent system compromise without the victim needing to click or meaningfully interact. The reported weakness stems from a trust-boundary failure in Anthropic’s Model Context Protocol (MCP) design, where the agent can autonomously chain data from a low-risk source (calendar content) into higher-privilege actions, potentially turning a benign user request (e.g., “take care of it”) into arbitrary local code execution.
Reporting indicates the exposure impacts 10,000+ active Claude Desktop users and 50+ extensions distributed via Anthropic’s extension marketplace. A key risk driver is that Claude Desktop/MCP extension components run unsandboxed with full host OS privileges, unlike typical browser extensions, meaning successful exploitation could allow reading arbitrary files, accessing stored credentials, and modifying system settings. One described proof-of-concept scenario involves inviting a target to a calendar event whose description embeds attacker instructions that the agent/extension chain may execute, demonstrating how routine productivity integrations can be weaponized at scale.
Mallory correlates global threat intelligence with your attack surface — know if you’re exposed before adversaries strike.
4 events from the most recent confirmed update back to the earliest known activity.
LayerX publicly detailed a proof of concept in which a malicious Google Calendar entry could cause Claude, after a vague user request such as reviewing calendar items and 'taking care of it,' to fetch code from a remote Git repository and download, compile, or execute it without confirmation. The disclosure characterized the issue as a workflow failure in autonomous agent decision-making rather than a traditional memory-corruption bug.
Anthropic told LayerX the reported behavior would not be fixed because it aligns with MCP's intended autonomy or falls outside the company's threat model, emphasizing that MCP servers are locally installed, user-enabled, and operate within the user's permission boundary. Subsequent reporting noted Anthropic framed MCP as a local development tool and placed responsibility on users to configure extensions securely.
After identifying the vulnerability, LayerX reported its findings to Anthropic. The disclosure described how Claude could chain low-trust external content into privileged MCP tools without explicit user approval, enabling zero-click remote code execution.
LayerX identified an architectural trust-boundary flaw in Anthropic's Claude Desktop Extensions/MCP ecosystem that could let untrusted connector data, such as a malicious Google Calendar event, trigger autonomous execution of attacker-controlled code through high-privilege local tools. The researchers said the issue could affect more than 10,000 active users and over 50 extensions, and rated it CVSS 10.0.
Vulnerabilities, threat actors, malware, products, organizations, and breaches Mallory has linked to this story.
4 references tracked. Mallory keeps watching after this page renders.
scworld.com
Open sourcetheregister.com
Open sourcetechrepublic.com
Open sourcecybersecuritynews.com
Open sourceMap indicators from this story to your assets and identify affected systems in minutes.
Every observed campaign, victim, and pivot linked to actors named in this story.
Malware, exploits, and IOCs connected to the activity described here.
YARA, Sigma, and Snort rules deployed to your SIEM as soon as they’re published.
Get matching new stories delivered to your team as they break — not the next morning.
Ask questions about this story and take action on the answers.
Other stories Mallory is tracking that overlap on entities, sources, or topic labels.
Researchers at Manifold disclosed two unpatched vulnerabilities in Anthropic’s **Claude for Chrome** extension that can let a malicious browser extension trigger Claude actions and access sensitive Google Workspace content, including **Gmail messages, Google Docs data and comments, and Google Calendar entries**. The researchers said the flaws were reported in May and remained reproducible in version `1.0.80`, with one issue allowing another extension that has script access on `claude.ai` to simulate a trusted user click and launch hardcoded Claude prompts on the victim’s behalf. The weaknesses stem in part from Anthropic’s earlier mitigation for **ClaudeBleed**, which limited prompts to pre-approved tasks but did not verify that task-triggering clicks came from a real user. Manifold also identified a separate design flaw in which Claude’s side panel can enter a privileged **no-confirmation** mode through a URL parameter, creating a potential privilege-escalation path if a future bug allows outside control of that parameter. The risk is highest when users enable Claude’s **“Act without asking”** mode, because the extension may perform actions without visible consent prompts; Anthropic acknowledged the reports but had not issued fixes, saying one issue was already tracked internally and the other was not externally reachable.
Jul 17, 2026
Researchers disclosed a critical zero-click vulnerability chain in Anthropic’s Claude Chrome extension that allowed a malicious website to inject prompts into the AI assistant without any user interaction. The attack relied on the extension trusting any `*.claude.ai` origin and a DOM-based XSS flaw in an older Arkose Labs CAPTCHA component hosted on `a-cdn.claude.ai`; by loading the vulnerable component in a hidden iframe and sending a crafted `postMessage`, attacker-controlled JavaScript could appear to come from a trusted Claude origin and submit prompts as the victim. Successful exploitation could have exposed more than 3 million users to account and data compromise, including theft of Gmail OAuth tokens, access to Gmail, Google Drive, and Claude chat history, and invisible actions such as sending emails on the user’s behalf. KOI Security researcher Oren Yomtov reported the issue to Anthropic in late December 2025, Anthropic patched the extension by tightening origin validation to `https://claude.ai` in January 2026, and Arkose Labs separately fixed the XSS issue in February 2026 after the vulnerable resource was disabled.
Jun 29, 2026
**Check Point Research** disclosed multiple critical vulnerabilities in Anthropic’s *Claude Code* AI coding assistant that could allow **remote code execution** and **credential theft** when a developer clones and opens an **untrusted repository**. The reported attack path abuses repository-controlled configuration and automation features (including **Hooks**, **MCP servers**, and **environment variables**) to trigger hidden shell command execution and to exfiltrate **Anthropic API credentials**, potentially enabling a pivot from a developer workstation into broader enterprise environments where Claude-related workflows and shared resources are accessible. The issues include consent-bypass and command-execution weaknesses tracked under **CVE-2025-59536** (covering closely related flaws involving repository configuration executing commands without adequate user consent) and an API credential exposure issue tracked as **CVE-2026-21852**, which affected *Claude Code* versions prior to **2.0.65** and enabled API key theft via malicious project configurations. Anthropic has **patched** the vulnerabilities and advised users to update to the latest version, while indicating additional hardening measures are planned to reduce supply-chain risk from malicious commits and repository-level configuration abuse.
Jun 29, 2026