Apache APISIX: Multi-auth preserves client-supplied Wolf identity headers

Authentication bypass by spoofing vulnerability in Apache APISIX.

On a route where multi-auth falls back from wolf-rbac to another successful authenticator, client-supplied Wolf identity headers can remain in the request. A downstream service that relies on those documented headers may therefore receive an identity that was not established by the successful authenticator.

This issue affects Apache APISIX: from 3.8.0 through 3.19.0.

Users are recommended to upgrade to version 3.20.0, which fixes the issue.