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Vary: Origin header (CORS caching)
The Vary header tells caches to store separate versions of responses based on request headers like Origin.
Why It Matters
Without Vary: Origin, CDNs might cache CORS responses with one origin and serve them for different origins, causing security issues or broken functionality.
How We Check
We verify that responses with dynamic CORS headers include `Vary: Origin` to ensure proper caching behavior.
How to Fix
Add Vary: Origin to any response that sets Access-Control-Allow-Origin dynamically based on the request.
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