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Graph/cors-auth-bypass-unauthenticated-api-calls

Pattern

Same-Origin Auth Bypass

cors-auth-bypass-unauthenticated-api-calls

A recurring auth model where the API relies on client-side or IP-only checks while cross-site requests (AJAX/CORS) enable attackers to call the API anyway, so the fix is to enforce real server-side authentication and authorization.

Node Details

Public graph metadata

Updated5/1/2026

Connections

30 linked nodes

Axios requests need to work on both client and server in Next.js while switching between DEVICE_TOKEN and AUTH_TOKEN for authentication

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?

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.

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.

RedirectResponse goes to "/" without the authentication cookie

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

Protect FastAPI routes so that authenticated users without the required permissions/roles cannot access specific endpoints.

The someone can easily append this query string to end of the page or fake the http referer to pretende to have paid for the product — in my getServerSideProps() function in my page, which is redirect from check out as determined by success_url. Tension: I need a server side check too. Outcome: How can I do that?

Checkout redirect can be faked by appending the success query string or spoofing the HTTP referer

Executing an authenticated AWS AppSync GraphQL mutation from a Next.js API route fails with `NoSignedUser: No current user` when using `generateClient()` from `aws-amplify/api`. Attempts to use `generateServerClientUsingCookies` also fail due to incorrect cookie handling/context.

After implementing login with NextAuth, the user session from `getServerSession(authOptions)` does not include a GitHub REST API access token, so API calls requiring a token fail.

I can still connect in ‘anonymous’ mode — I'm trying to set up authentication for my OPC-UA server. Tension: I don't want my clients to be able to connect to my server in ‘anonymous’ mode. Outcome: the certificate login is blocked, which is fair enough.

A SPA calls a backend API (B) which must call another downstream API (C) on behalf of the signed-in user. The question is how to pass/obtain appropriate tokens so B can call C without unsafe or inappropriate token handling (e.g., forwarding an identity token).

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.

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.

Whether a user can manipulate or forge React component props to bypass the intended one-way data flow between components.

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

Uncertainty whether an authorization code in a native app should be exchanged for an access token client-side or backend-side, and whether the resulting external access token can be used to authorize calls to the app's own Web API.

As you only check the IP, this works and the attacker can now execute API calls against your application. — an attacker has control of a malicous site. Outcome: Defending against this requires authentication of the requests to the API.

handling endpoint authentication of Entra to custom SCIM endpoint. Outcome: And I can't understand why this line was added.

authorization code injection attacks against confidential clients

Client-side double-submit CSRF token generation is vulnerable to subdomain hijacking

httpOnly cookies are the best way to store tokens safely and protect them from XSS attacks — storing JWTs on the client. Tension: JavaScript won't be allowed to read httpOnly cookies. How would the client handle routes authentication? Outcome: The browser won't automatically set the `Authorization` header like it does with cookies.

the code verifier is sent to the authorization server from the client-side of the application — implementing OAuth2 with authorization flow + PKCE for a single page web application. Tension: doesn't that mean the code verifier is exposed? Outcome: PKCE protects against a specific vulnerability.

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.

If it contains a specific X-API-Key value, then proceed otherwise return unauthorized. — write a simple HttpServerFilter that would check the incoming http request headers. Tension: Given the return is a Publisher, how could this be achieved? Outcome: I have this code instead this works.

Swagger UI API requests need an Authorization bearer token header for SSO, but the attempted fetch event interception does not catch the outgoing requests.

Whether putting sensitive API keys in Next.js .env.local and referencing them in getStaticProps/getServerSideProps could expose the secrets to browser users.

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