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Graph/cross-origin-blocked-requests

Pattern

Cross-Origin Request Rejection

cross-origin-blocked-requests

Origin/URL mismatches between frontend, API/proxy, and redirect/SSL layers cause browsers and reverse proxies to reject requests—especially WebSockets—leading to blocked API calls, failing first handshake, and redirect-limit errors when HTTPS and trusted origins don’t align.

Node Details

Public graph metadata

Updated7/28/2026

Connections

30 linked nodes

Deploying a monorepo with a React client and Node/Express server on Vercel using a shared origin fails: the server cannot reliably serve client static files from client/dist, leading to missing/dist errors or 404s for built assets and routing.

Access to fetch at 'https://askida-backend.vercel.app/payment/create' from origin 'https://www.asunatech.com' has been blocked by CORS policy — from origin 'https://www.asunatech.com'. Tension: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Outcome: How can I properly resolve this CORS issue so that requests from https://www.asunatech.com to my backend are allowed?

"x-forwarded-host`header with value`foobar-3000.app.github.dev`does not match`origin`header with value`localhost:3000` from a forwarded Server Actions request. Aborting the action.". Tension: the problem is occurring elsewhere in the application. Outcome: Aborting the action.

Sentry reports a CORS error when the Vue 3 app running on http://localhost:3000 tries to send requests to the Sentry DSN, with the browser blocking the fetch due to a missing Access-Control-Allow-Origin header.

requests with the forbidden fields sailed through to the write path. Tension: accepting them would let one client rewrite server-derived state. Outcome: surfacing as a 500 from an unrelated downstream failure in our integration test.

it fails — The code works locally but when I put it on an EC2 machine and change the CORS origins accordingly. Tension: I've checked the URL for 2 hours straight. Outcome: Still the same error below.

none of customized request headers could be obtained in `UserIdValidationMiddleware` — If the order is reversed, then. Tension: It is not on the axios side. Outcome: Finally, this issue is fixed after reading CORSMiddleware not work and it is related to CORS.

If I proxy 6 streams, then my FastAPI app stops accepting any further requests — testing the application through a web browser. Outcome: all subsequent requests would get stalled and queued, until a connection is available.

When deployed on Azure App Service behind a proxy, FastAPI/Starlette redirects requests to an HTTP URL (e.g., HTTP Location header in a 307) instead of preserving HTTPS. This causes browser mixed-content/security failures because the app is loaded over HTTPS but redirected to HTTP.

When I send an HTTPS request using the Swagger UI. Tension: the redirection then fails. Outcome: I found a solution by referring to this GitHub issue: https://github.com/encode/uvicorn/issues/369.

AADSTS9002325: Proof Key for Code Exchange is required for cross-origin authorization code redemption. Tension: redirects uris not matching.

axios made the requests to `http://sub.domain.tld/api/path`, while my reverse proxy forwarded that to the IP:Port

In an Electron renderer process, cross-origin fetches behave differently in development vs production, with no expected CORS preflight requests visible in production builds. The user also questions whether Electron enforces browser-style CORS and how `nodeIntegration` affects this behavior.

Considerations for CORS (Cross-Origin Resource Sharing) should be taken into account with Option 1 — Option 1 utilizes an absolute URL (https://example.com/project_folder/user) for making AJAX calls. Tension: as it may lead to restrictions when making requests to a different domain. Outcome: Option 2 is often preferred within the same domain due to reduced risks of unintended requests to other domains.

callback request is not secure enough for production

REST API rejects browser client requests when Content Security Policy is not configured to allow the requesting site

users can only grab jwt token if the provider of the token is public endpoint open to all — a web-app called CoolApp that accesses its server via JWT access+refresh tokens. Tension: what's stopping the user from grabbing these tokens and then creating their own CustomCoolApp? Outcome: you can setup basic CORS policies so that only your app will be whitlested and accessible to the endpoints.

Frontend and API subprojects need secure access control so unauthorized apps cannot use the API

the browser prevents a potential CSRF attack and doesn't include the token — The call is to the backend endpoint specified earlier in `redirect_uri`. Tension: I need a browser to include the `ASP.NET_SessionId` cookie in the request. Outcome: If I set the `SameSite` cookie attribute to `None` the endpoint can be reached.

The Heroku-hosted MERN app receives many automated-looking requests from the same forwarded IP in the same second, with suspicious query/path content (e.g., unexpected “if”/“php” strings). This behavior appears to be scanning or an attack proxy and raises concerns about security and abuse.

Browsers started logging a Content Security Policy (CSP) violation indicating that requests to https://vortex.data.microsoft.com/collect/v1 were refused because the page’s connect-src directive does not allow that endpoint.

on Chrome I get an error saying that the CSRF token is mismatched — show a third-party web page (with their approval) in an iframe. Tension: This site has a different domain to my parent site. Outcome: The site displays fine on firefox.

a single Cypress test cannot span across multiple origins — we are just trying to test that clicking that button redirects to the correct URL. Tension: instead of allowing the redirect and attempting to read the new URL, we tried to stub the redirect, block it and read what the application is trying to. Outcome: Once the stub is in place, I clicked the button to invoke the method.

Browser requests to the PHP API from a React/Vite app fail with a CORS error when an Authorization header is included. Requests without custom headers work correctly.

Accessing https://example.com results in a “too many redirects” loop, while other domain variants redirect correctly for a React app served by Apache with Cloudflare-managed DNS/SSL.

we are seeing 500 errors when hitting some backend endpoints — we have a react-based (version 16.14.0) PWA that is hosted on Microsoft Azure app service plans (premium tier). Tension: It is ONLY affects POST endpoints. GET endpoints successfully continue to work to these backends. Outcome: Current workaround is to change your app service to use http 1.1.

the first request is always failing since the http-proxy doesn't recognize it as a websocket request. Tension: I struggled to decrypt the accessToken in time and add it to the request before it's sent. Outcome: for now it's not bothering me that much.

Requests to the Django/DRF backend fail with “CSRF Failed: Origin checking failed - http://localhost:8000/ does not match any trusted origins.”

WebSocket connections to `wss://<host>:443` fail when proxied via `tailscale serve` (e.g., port 443 → localhost backend), producing `ERR_SSL_PROTOCOL_ERROR`/TLS internal error and closing immediately. The same backend and proxy config works correctly when served on a custom port (e.g., 8443).

Wget before 1.21.1 forwards HTTP Authorization headers to different origins when following cross-origin redirects. — when following cross-origin redirects. Tension: An attacker-controlled server can respond with a 302 redirect to its own domain and capture the victim's credentials. Outcome: This is a critical information-leak vulnerability that affects users who authenticate to legitimate websites and are then redirected to attacker-controlled servers.

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