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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.
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Anthropic acknowledged Manifold's reports but did not ship fixes. According to the reporting, the company said one issue was already internally tracked and the other was not externally reachable.
Researchers at Manifold reported two vulnerabilities in Anthropic's Claude for Chrome extension in May 2026. The issues involved simulated trusted clicks that could trigger Claude actions and a side-panel no-consent mode reachable via a URL parameter.
Manifold reported that two vulnerabilities in Claude for Chrome remained exploitable despite eight subsequent releases, including version 1.0.80. The flaws could let a malicious extension trigger Claude actions and expose Gmail, Google Docs, and Google Calendar data, especially when 'Act without asking' is enabled.
Anthropic released Claude for Chrome version 1.0.80 on July 7, 2026. Manifold said both previously reported vulnerabilities were still reproducible in that release.
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Researchers at LayerX disclosed a critical flaw in Anthropic’s Claude Chrome extension that allowed **any other Chrome extension**, including ones with no declared permissions, to send hidden instructions to Claude and abuse its browser automation features. The issue reportedly stemmed from the extension trusting messages associated with the `claude.ai` origin without properly authenticating the true sender, creating a cross-extension privilege escalation path. In proof-of-concept attacks, LayerX said it used the weakness to extract files from Google Drive, read and send Gmail messages, steal code from connected private GitHub repositories, and even summarize or delete recent emails to conceal activity. Anthropic said the bug had already been identified internally and released version `1.0.70` with mitigations, including approval flows for privileged actions, but LayerX reported that the fix was incomplete and that takeover remained possible through privileged mode and side-panel initialization paths. The researchers said the flaw exposed a broader trust-boundary problem in AI browser assistants, where interface-based approvals and safety guardrails can be bypassed if extensions fail to verify message origin and execution context. Separate White House discussions about tighter oversight of advanced AI models, including Anthropic systems with offensive cyber capabilities, underscored growing concern over how powerful AI tools are secured before deployment.
Jun 29, 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
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.
Jun 29, 2026