

I do believe keycloak does the same. In keyCloak one would create a client application service. Here one will provide valid redirect URIs. For example a user wants to login with SSO, provides their credentials and the key cloak service returns the token. Than the user will be redirected to the valid redirection target. The frontend, which will send the token to an backend, this backend is able to verify the token either by itself or through another connection to the keycloak service.
I see. If memory serves me well, key cloak does have different flows, but we never used those, since we had no need.
So yeah, that’s bad.