Add extra safety checks for proto pollution

[jacob314]

Summary

Add defensive checks to make the object deep merge safer.

[gemini-cli]

Hi @jacob314, thank you so much for your contribution to Gemini CLI! We really appreciate the time and effort you've put into this.

We're making some updates to our contribution process to improve how we track and review changes. Please take a moment to review our recent discussion post: Improving Our Contribution Process & Introducing New Guidelines.

Key Update: Starting January 26, 2026, the Gemini CLI project will require all pull requests to be associated with an existing issue. Any pull requests not linked to an issue by that date will be automatically closed.

Thank you for your understanding and for being a part of our community!

[gemini-code-assist]

Summary of Changes

Hello @jacob314, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the security of the deepMerge utility by introducing robust checks to prevent various forms of prototype pollution. The changes ensure that malicious input attempting to modify object prototypes via __proto__, constructor, or prototype keys is safely ignored, thereby protecting the application from potential vulnerabilities. Comprehensive tests have been added to validate these new safeguards.

Highlights

• Security Enhancement: Implemented additional checks in the deepMerge utility to prevent prototype pollution by explicitly ignoring constructor and prototype keys during the merge process.
• Test Coverage: Expanded the existing prototype pollution test suite to include new test cases specifically targeting constructor and prototype keys, ensuring the new safety measures are effective.

Changelog

• packages/cli/src/utils/deepMerge.test.ts
  • Expanded prototype pollution test to cover constructor and prototype keys.
• packages/cli/src/utils/deepMerge.ts
  • Added checks to skip constructor and prototype keys during deep merging to prevent prototype pollution.

Activity

• No activity has been recorded for this pull request yet.

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[gemini-cli]

Hi there! Thank you for your contribution to Gemini CLI.

To improve our contribution process and better track changes, we now require all pull requests to be associated with an existing issue, as announced in our recent discussion and as detailed in our CONTRIBUTING.md.

This pull request is being closed because it is not currently linked to an issue. Once you have updated the description of this PR to link an issue (e.g., by adding Fixes #123 or Related to #123), it will be automatically reopened.

How to link an issue:
Add a keyword followed by the issue number (e.g., Fixes #123) in the description of your pull request. For more details on supported keywords and how linking works, please refer to the GitHub Documentation on linking pull requests to issues.

Thank you for your understanding and for being a part of our community!

[github-actions]

Size Change: +46 B (0%)

Total Size: 25.9 MB

ℹ️ View Unchanged

Filename	Size	Change
./bundle/gemini.js	25.4 MB	+46 B (0%)
./bundle/node_modules/@google/gemini-cli-devtools/dist/client/main.js	221 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/_client-assets.js	227 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/index.js	11.5 kB	0 B
./bundle/node_modules/@google/gemini-cli-devtools/dist/src/types.js	132 B	0 B
./bundle/sandbox-macos-permissive-open.sb	890 B	0 B
./bundle/sandbox-macos-permissive-proxied.sb	1.31 kB	0 B
./bundle/sandbox-macos-restrictive-open.sb	3.36 kB	0 B
./bundle/sandbox-macos-restrictive-proxied.sb	3.56 kB	0 B
./bundle/sandbox-macos-strict-open.sb	4.82 kB	0 B
./bundle/sandbox-macos-strict-proxied.sb	5.02 kB	0 B

_{compressed-size-action}

[gemini-code-assist]

Code Review

This pull request enhances security by adding extra checks to prevent prototype pollution in the customDeepMerge utility. The changes block merging of constructor and prototype properties, in addition to the existing __proto__ check. Corresponding unit tests have been added to verify this behavior. The implementation is correct and follows security best practices.