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security: iframe sandbox allows same-origin access to parent page

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#3 2 comments 0 reactions 0 assignees View on GitHub

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Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Quiet
Tech stack
typescript
Domain
frontend, security

Research direction

Start at apps/app/src/components/generative-ui/widget-renderer.tsx:523 and inspect how the iframe sandbox and postMessage bridge are configured. Test what breaks when allow-same-origin is removed, including any CDN or fetch behavior mentioned in the issue. Done means the sandbox uses only the permissions required by the renderer, the bridge still works, and the intentional security tradeoff is documented if the permission must remain.

Written by the indexing model from the issue text.

Description

bug

Description

Severity: P0 — Security

In apps/app/src/components/generative-ui/widget-renderer.tsx:523, the iframe sandbox attribute is:

sandbox="allow-scripts allow-same-origin"

The combination of allow-scripts + allow-same-origin allows the iframe to access window.parent and all parent DOM/cookies. While the CSP mitigates remote script loading, agent-generated HTML with inline scripts has full same-origin access to the host page.

Failure mode

XSS via agent-generated content — malicious or hallucinated HTML could read/modify parent page state, steal cookies, or call CopilotKit APIs.

Suggested fix

Remove allow-same-origin from the sandbox. The iframe only needs allow-scripts. The postMessage bridge already works cross-origin. If allow-same-origin is truly required (e.g., for CDN fetches), tighten CSP connect-src and document the tradeoff.

Open question

Is allow-same-origin intentional? What breaks if it's removed?

From self-review finding F01

Dominant language
TypeScript
Stars
1.6k
Forks
202
PR merge metrics
No merged PRs in 30d

Contributor guide

Open the contributing guide

First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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