Vulnerability in Anthropic Claude Dispatch Allowed Browser Extensions to Execute Code on Host Machine
Security researchers publicly disclosed a vulnerability in Anthropic’s Claude Dispatch feature on 6 November 2026. The flaw allowed a malicious browser extension to send instructions to the Claude Desktop agent exactly as if they had come from the user, resulting in arbitrary command execution on the machine running the desktop application.
Claude Dispatch is part of the Cowork suite and appears in the side panel of the desktop client. It enables users to forward tasks from a mobile device to the desktop instance. The root cause was excessive trust placed in any authenticated session on claude.ai; no visible page element or cryptographic binding verified that the browser tab was legitimately paired with the local application.
The attack required three conditions: a browser extension granted script-execution permission on claude.ai, a user logged into both the website and Claude Desktop, and Dispatch enabled with the desktop application open. Under these conditions the extension could open the Dispatch panel and issue repeated requests—such as installing an npm package—while automatically clicking permission prompts every second. The agent initially hesitated but proceeded after a follow-up insistence message.
The researchers chose an innocuous npm package that simply opened the Calculator application. They noted that the same workflow could be used to steal files or install a persistent backdoor because the agent already possessed the necessary local privileges. No in-the-wild exploitation has been observed; all testing occurred in a controlled laboratory environment.
The report also highlighted that personal accounts with cross-device Dispatch enabled on corporate laptops created an additional risk: a compromised personal browser extension could reach the employer’s machine. Similar attack paths exist via Claude Code Remote Control and Cowork sessions, although no public proof-of-concept was released for those vectors.
The vulnerability was reported to Anthropic on 14 May 2026. The company validated the submission on 19 May and closed it as a duplicate of an internally identified issue. On 13 October the vendor informed researchers that Dispatch would be retired by the end of the month. By 6 November the feature was closed to new users, although existing subscribers on certain paid plans retained access.
Researchers advise users to disable Dispatch between devices when it is not required, to review and remove paired devices regularly, and to treat any browser extension with the same caution as locally installed software. They also recommend monitoring all actions performed by the AI agent on the endpoint.
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