Shared from twixb · simonwillison.net

CSP Allow-list Experiment

simonwillison.net·May 13, 2026

The CSP Allow-list Experiment demonstrates how to load an application in a CSP-protected sandboxed iframe and utilize a custom `fetch()` function to intercept CSP errors, allowing users to add domains to an allow-list and refresh the page. This tool aims to enhance user experience by simplifying CSP management.

The CSP Allow-list Experiment demonstrates an innovative method to handle CSP errors in a sandboxed iframe by using a custom `fetch()` function to communicate with the parent window. This approach could be particularly beneficial for enhancing security measures in AI coding tools like Claude Code or Codex, where sandboxing and secure data fetching are essential. Consider integrating similar mechanisms in your AI development processes to improve secure data handling and user interaction.

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