Google Chrome Extension Claude Bleed Vulnerability Exposes Users' Sensitive Data

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The ClaudeBleed Vulnerability: A Critical Security Issue

The ClaudeBleed vulnerability compromises the security of the Claude for Chrome browser extension, allowing hackers to bypass guardrails and steal private data.

Trust Boundary Violation

Researchers from LayerX discovered the issue, which stems from a critical trust boundary violation caused by the extension’s failure to properly identify the source of incoming messages.

According to researchers, “the extension’s failure to properly identify the source of incoming messages allows any script running on the claude.ai website to send commands to the extension, effectively turning it into a ‘confused deputy’ that performs malicious tasks under the guise of legitimate activity.”

Exploitation Techniques

LayerX created a fake extension that forces Claude to access a user’s Google Drive and share sensitive files with an external address.
The team bypassed the built-in guardrails of Claude’s Large Language Model (LLM) through approval looping and DOM manipulation techniques.
Hackers can deceive the extension into performing unauthorized actions, such as summarizing private messages and deleting evidence.

Patch and Circumvention

After being notified of the vulnerability, the vendor, Anthropic, released a patch in version 1.0.70. However, the LayerX team quickly discovered that this fix could be easily circumvented by exploiting the extension’s privileged mode, known as “Act without asking mode.”

According to researchers, “this raises concerns about the speed at which AI vendors grant powerful capabilities without adequately addressing fundamental security issues, leaving users vulnerable to exploitation.”

Underlying Problem

Researchers emphasize that the underlying problem of origin-based trust remains unresolved and can be abused to bypass the patch and exploit the Claude for Chrome extension.

This highlights the need for more robust security measures to prevent similar vulnerabilities in the future.