Unpatched Claude for Chrome Flaw Lets Extensions Read Gmail, Calendar

AI security firm Manifold says two vulnerabilities it reported to Anthropic in May remain exploitable in the latest version of Claude for Chrome, the company’s agentic browser extension.

According to Manifold, the flaws let a malicious browser extension trigger Claude into taking actions on a user’s behalf without any genuine click or approval from the victim. An attacker could exploit them to read Gmail messages, Google Docs documents, and calendar entries.

The core issue is related to a fix Anthropic shipped earlier this year in response to a similar vulnerability dubbed ClaudeBleed. That update restricted which prompts an outside webpage could feed into Claude, narrowing the extension’s exposure to a fixed set of pre-approved tasks.

Manifold found that the mechanism used to activate those tasks doesn’t verify whether a click actually came from a real user, meaning another extension can fake the interaction and set the process in motion.

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