https://shipreadyai.dev/learn/findings/o13-cors-open-credentials

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# Any site can read your responses with a visitor's session

{path} answered a request from an outside origin with an allow origin of {origin} and credentials allowed, so a page on another domain can read responses using your visitor's session.

## Why AI-built apps get this

Cross origin rules get widened during development, when a local page needs to talk to a deployed backend. The wildcard that unblocked the afternoon stays in the deployed version, because nothing about it fails afterwards.

## Evidence line

GET /api/ with an outside origin returned access-control-allow-origin: * with credentials allowed

## The fix

Replace the reflected origin with a fixed list of your own addresses, or turn credentials off for cross origin requests.

## Prompt

Replace the reflected cross origin allow header with an explicit list of allowed origins, and only allow credentials for those origins.