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Graph/cross-subdomain-cookie-isolation

Pattern

Cross-Subdomain Cookie Isolation

cross-subdomain-cookie-isolation

Cookies fail to authenticate or authorize across frontend/backend and redirect flows because default cookie domain and SameSite/HTTPOnly settings isolate them, leaving JS unable to read tokens and browsers refusing to send cookies on third-party contexts.

Node Details

Public graph metadata

Updated7/7/2026

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

Cookie “__vercel_live_token” has been rejected because it is in a cross-site context and its “SameSite” is “Lax” or “Strict” — deployed it on Vercel. Tension: But i setup cookies in my project like this. Outcome: Then you need to use https://localhost:5000 and not http://localhost:5000.

When the UI calls the `POST /auth/callback/passkey` endpoint. Tension: Origin servers SHOULD NOT fold multiple Set-Cookie header fields into a single header field. Outcome: Cloudflare seem to be in the wrong here.

when I refresh my page the cookie gets deleted — I have deployed my sveltekit frontend and python flask backend on vercel. Tension: On localhost, they worked just fine however when I deployed it, the cookies were not persistent. Outcome: it does sets the cookie, but on refresh, the cookie gets disappeared.

Using Fetch from my `index.html` from my `portal.mydomain.com` does not. — Enter `api.mydomain.com` into a browser directly does save my cookie. Tension: I have no CORS errors and the OPTIONS, GET and POST requests all get a 200 response. Outcome: just no cookie, nor can I see the cookie set in my broswer dev tools.

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

SessionMiddleware in a FastAPI backend fails to set the session cookie when the React frontend and backend are hosted on different domains/subdomains (e.g., XXX-ui.fly.dev vs XXX-api.fly.dev). The browser rejects the cookie with an 'invalid domain' error and no session is maintained.

were not accessible in js and in browser — Cookies are being set and sent with the next request. Outcome: The problem solved by adding `domain="blueberry.adefe.xyz"` to the cookie in response.

MissingKeyMissing Key-Pair-Id query parameter or cookie value — {urn}/manifest/{derivativeurn}/signedcookies. Tension: I get the following error that suggest I'm missing a header.

Embedding a CPQ web app as an iframe inside Salesforce fails to persist authentication cookies/session for API calls. Login in a new tab isn’t recognized inside the Salesforce iframe, preventing authorized requests.

Allowing users to upload and embed their own web components as dashboard widgets, while preventing them from accessing cookies or other data on the hosting page without manually auditing each widget.

the cookie will be specifically set with `domain=app.sunsetland.com.au`. Tension: if we were to host another subdomain aside from `app.`, we actually would likely encounter the reCAPTCHA challenge again.

can I create, from 2. and 3. a server side httpOnly cookie (containing a `widget_id`) of domain `mycompany-example.com`, that can be used during step 5. Outcome: when the user visits our website so we know which widget they come from ?

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

Confusion about cookie authentication versus token authentication

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 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.

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.

If I check 'Remember Me' in form, this add a cookie with name "REMEMBERME". Tension: I'm implementing custom authenticator. Outcome: your cookie is normal.

The session identifier (req.sessionID) changed on every subsequent HTTP request from the React client to the Express server, preventing consistent session persistence.

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.

Clicking the SSO button does not redirect the user to the /home page after authentication, and MSAL token generation does not occur. The app stays on the same page without completing the login flow.

req.cookies.jwt is defined in localhost but undefined in deployment — The cookies are being set in the browser. Tension: the only problem is I can't access them. Outcome: Here to ken is undefined.

After signing in, middleware redirection occurs, but the browser URL remains unchanged (e.g., it doesn't update to the intended callback/protected route).

The browser does not store the refresh token cookie returned by the Django Ninja login endpoint, even though the cookie appears in the response headers and the fetch call uses credentials: 'include'.

one is working without any credential or cookie[SessionId] but another one is not working — two api's in my spring mvc project which have identical structure. Tension: while calling using Postman or while hitting the APIs in browser/UI project.

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

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.

throws "Cookies can only be modified in a Server Action or Route Handler" — called from Next.js 15 Server Components (pages, layouts). Tension: The error appears intermittently — only when the session needs refreshing (controlled by `updateAge` config). Outcome: With `updateAge: 300` (5 minutes), it crashes every ~5 minutes for active users.

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