[Python] Iframe Authentication Issue: 401 Unauthorized for Private APIs (React Frontend,...

I'm embedding my React.js application (with a Python backend) into another website via an iframe. While public APIs work fine, private API calls consistently return 401 Unauthorized errors, and the user gets logged out. My backend uses session cookies for authentication.

I suspect this is due to browser security restrictions like the Same-Origin Policy and the SameSite cookie attribute.

My Setup:

Frontend: React.js Backend: Python (Flask, but framework-agnostic advice is welcome) Auth: Cookies.

The Problem:

Private API requests from the iframe fail with 401 Unauthorized.

What I'm Looking For:

I need guidance on how to properly configure my setup to allow authenticated requests from the iframe:

1. 
   Python Backend (Cookies): How do I configure session cookies with SameSite=None; Secure in a Python backend to work cross-origin?
   
   
2. 
   Python Backend (CORS): What's the correct CORS setup for my backend, specifically regarding supports_credentials for the parent domain?
   
   
3. 
   React Frontend: Any specific fetch or Axios configurations needed to send credentials from within an iframe?
   

Alternatives: If cookies are too problematic, what are secure alternatives (e.g., passing JWTs via window.postMessage) and their workflow? My application will be served over HTTPS.

Any code examples or best practices would be greatly appreciated! Thanks!

I've attempted a basic iframe embed, expecting normal authenticated behavior, but instead, I'm facing 401 Unauthorized errors and session loss. My research points to CORS and SameSite=None; Secure cookies as solutions, but I'm unsure of the precise implementation details for my Python backend and React frontend (e.g., supports_credentials for CORS, or configuring fetch/Axios to send credentials).

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