Simon Willison’s Weblog

14th March 2026

Research CSRF Protection Demo: Modern Browser-Based Defenses — Modern browser security now enables robust Cross-Site Request Forgery (CSRF) prevention without requiring tokens. This demo project contrasts a vulnerable FastAPI bank app with a protected version, showcasing how browser-sent headers like `Sec-Fetch-Site` and `Origin` empower servers to automatically reject cross-origin POST requests.

Posted 14th March 2026 at 4:34 am

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This is a beat by Simon Willison, posted on 14th March 2026.

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