Yes, it doesn’t look to be documented (here:
https://github.com/pact-foundation/pact-reference/tree/master/rust/pact_verifier_cli#state-change-requests) but in the state change requests, you will receive a payload with the provider state and any parameters (this endpoint will be called once per state for each tests i.e. there is a many-to-one relationship of states to tests).
In the response to a state change URL, you can respond with a JSON object with any injected values. The keys in that JSON must match the keys for the value to be injected