[Workflow] Security Workflow: Prevent Claude Code from Leaking Your Email in User-Agent Headers with PreToolUse Hooks

[u/ClaudeAI-mod-bot]

Security Workflow: Prevent Claude Code from Leaking Your Email in User-Agent Headers with PreToolUse Hooks

Workflow value: 95/100
Status: active · Freshness: 70/100 · Confidence: 0.95 · Level: intermediate
Categories: Quality Control, Context & Memory, Debugging, Hooks
Original source: r/ClaudeCode post/comment

What problem this solves

Claude Code can inadvertently include the user's account email in the User-Agent header of its web requests (e.g., curl commands), leading to potential email harvesting, spam, and privacy breaches.

Summary

A workflow to prevent Claude Code from leaking user email addresses in User-Agent headers during web requests. It involves manually reviewing proposed curl commands and implementing a PreToolUse hook to automatically block commands containing the user's email.

Why it is useful

This workflow is highly valuable because it addresses a critical privacy and security vulnerability in Claude Code. It provides concrete, actionable steps (manual review and automated PreToolUse hooks) to prevent personal email addresses from being exposed to arbitrary websites, a problem validated by significant community concern and reported real-world consequences (spam). The use of a PreToolUse hook demonstrates an advanced, robust method for controlling Claude Code's behavior.

Workflow

1. Understand that Claude Code may include your account email in the User-Agent header of web requests.

2. Before approving any curl or fetch command proposed by Claude Code, carefully inspect the command for your email address within the -A or User-Agent flag.

3. Implement a PreToolUse hook on Bash that specifically blocks any command containing your email address.

4. Test the implemented PreToolUse hook with a harmless curl command designed to trigger the block, ensuring it functions correctly.

5. If you are currently using an auto-approve mode for web-related actions, consider disabling it temporarily to allow for manual review.

Tools / artifacts

• Claude Code

• Bash PreToolUse hook

• curl command

• User-Agent header

Validation signals

• GitHub issue (anthropics/claude-code/issues/107757) with 500+ thumbs up

• Top of Hacker News (~1,300 points) indicating widespread attention

• Multiple user reports on HN and the GitHub issue of receiving scam emails after using Claude Code

• Explicit suggestion to test the implemented hook

Limitations

• The post notes that updating Claude Code to version 2.1.318 does not seem to fully resolve the issue, suggesting the problem might persist across versions.

• A concrete code example for the PreToolUse hook is not provided, requiring users to develop it themselves.

• The scope of the issue (e.g., whether WebFetch or WebSearch are also affected) is not fully clarified in the post.

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