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Stripe.js and CORS: Payment Element, cross-origin iframes, and 3DS flows that depend on postMessage, not your API
Your REST API may be same-origin while Stripe-hosted fields live on stripe.com—CORS on your server rarely fixes iframe failures.
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stripepaymentscors
Webhooks
Webhook endpoints are server-to-server; configure signing secrets and ignore browser CORS entirely for those routes.
Idempotency keys on PaymentIntents protect against duplicate charges when clients retry after network blips.
Connect platforms
Express accounts may use different redirect URLs—test OAuth flows across all allowed origins.
Platform liability differs from direct charges—document which origin hosts the checkout UI.