A new cybersecurity revelation highlights the risks that come with the rapid integration of artificial intelligence tools into browsers. Researchers at security firm LayerX have identified a serious vulnerability in the Claude extension for Google Chromethat could allow malicious actors to gain control of the AI assistant and use it as a tool to steal data or perform actions without the user’s consent.
The vulnerability, dubbed ClaudeBleed, exposes a critical issue in the way the extension handles communication with other scripts running within the browser environment.
Claude: How the ClaudeBleed vulnerability works
According to LayerX, the problem arises from a combination of incomplete security checks and misplaced trust in the origin of the command, rather than in the actual execution environment.
Simply put, the Claude extension appears to accept commands from any script running on the claude.ai, without checking whether it comes from a legitimate process or a malicious third-party extension.
See also: Critical vulnerability in Claude Code comes after code leak
This means that an attacker could create a seemingly innocent Chrome extension without special access rights, which would still be able to communicate with Claude and issue commands to it with elevated privileges.
The researchers explain that the extension essentially trusts the identity of the domain and not the actual source of the command, creating a dangerous security hole.
From productivity assistant to attack tool
The most worrying aspect of the case is that the vulnerability could turn Claude from a productivity tool into a cyberattack mechanism.
LayerX demonstrated that through specially crafted prompts, an attacker can manipulate the AI agent to gain access to services such as Gmail, GitHub, and Google Drive, performing actions on behalf of the user.
Possible attacks include:
- sending emails without the user's knowledge
- delete files
- document content export
- sharing sensitive information
- access to repositories and source code
This practice is a new form of attack that leverages the automation of artificial intelligence itself.
Bypassing protective mechanisms
Although Claude has confirmation mechanisms for sensitive actions, LayerX managed to bypass them.
See also: OpenClaw and Claude store AI-generated podcasts on Spotify
The researchers used repeated confirmation message, combined with DOM, to alter the interface and mislead the system.
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This way, the extension could “believe” that the user had approved an action, when in fact, this had not happened.
The ability to alter the visual representation of actions creates a new level of risk, as the user may never realize that the AI agent has already acted.
Anthropic's reaction
After the vulnerability was responsibly disclosed, Anthropic issued a patch. However, according to LayerX, the patch only addresses part of the problem. The fix limits remote commands to “standard” mode, without eliminating the underlying architectural weakness.
Even more worrying is the fact that an attacker can transfer the extension to 'privileged' mode, bypassing the protection without any notification to the user.
The broader issue of AI agent security
The ClaudeBleed case is not just about a browser extension. It represents a broader challenge that accompanies the new generation of AI agents with executive capabilities.
As more and more tools gain access to emails, cloud files, repositories, and personal data, security requirements become dramatically stricter.
See also: Fake Claude website distributes new “Beagle” malware
The incident shows that the security of these systems cannot be based solely on traditional browser isolation mechanisms. A new security design is required, specifically adapted to the era of AI assistants.
For users, the message is clear: installing AI extensions should be accompanied by increased caution, periodic permissions checks, and prompt application of security updates.
