Monthly Quick Tips

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Hey folks! This is the first in an ongoing series designed to provide monthly quick tips on trending search terms in the community. Here are a handful from the past month:

has been blocked by cors policy: response to preflight request doesn't pass access control check: it does not have http ok status.

  • ​​Double-check that the “Allowed Web Origins” and “Allowed Origins (CORS)” fields in your Auth0 settings include the domain from which the request originates.

  • If you are running your application locally, ensure that the local host and port are also added to the Auth0 CORS settings.

proof key for code exchange is required for cross-origin authorization code redemption.

This error suggests that your application is expected to implement the PKCE (Proof Key for Code Exchange) flow for added security. This is particularly important for OAuth/OIDC applications that run on a user’s device and don’t have a backend to keep secrets safe.

PKCE adds an additional layer of security by generating a unique, temporary code (the “code verifier”) on the client side at the beginning of the authentication process. This code is then transformed into a “code challenge,” which is sent alongside the authorization request. When exchanging the authorization code for an access token, the original “code verifier” must also be sent to prove that the client making the request is the same one that initiated the authorization code request.

the provided redirect_uri is not in the list of allowed callback urls.

This error typically occurs when you’re integrating Auth0 with OAuth/OIDC and the URL to which you’re trying to redirect after authentication is not listed in the “Allowed Callback URLs” field in your Auth0 settings.

  • Exact Match: The redirect_uri specified in your request must exactly match one of the URLs listed in the Allowed Callback URLs field in your Auth0 Application settings.

  • The Protocol Matters: Make sure that the protocols (http or https) are the same in both the “Allowed Callback URLs” and your request.

  • Trailing Slashes: Be aware of trailing slashes. https://example.com/callback and https://example.com/callback/ are different URLs.

failed to fetch. possible reasons: cors network failure url scheme must be "http" or "https" for cors request.

  • Check your browser’s console logs and network tab for more details on the failed request.

  • Make sure CORS is configured correctly on the Auth0 dashboard and in your server settings.

  • Verify the URL scheme to make sure it’s either HTTP or HTTPS.

jsonwebtokenerror: invalid signature

This can be a bit of a tricky error to troubleshoot, but here are a couple things to check:

  • Secret Mismatch: The secret key used to verify the JWT signature on your server doesn’t match the one used to sign the token by Auth0.

  • Algorithm Mismatch: The algorithm specified in your verification method doesn’t match the algorithm used for signing by Auth0 (think RS256).

  • Configuration Issues: Incorrect Auth0 client settings and/or domain could also lead to this error.

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