Double spring security filter registration

You can use the basic demo application of Baeldung to see the behaviour: https://github.com/eugenp/tutorials/tree/master/spring-boot-modules/spring-boot-keycloak   Just add a breakpoint in the VirtualFilterChain (inner class of Springs FilterChainProxy) "doFilter" method. Now inspect the "additionalFilters" and "originalChain.filters" variables. Normally, the filters in the "originalChain" should be disjoint from the additionalFilters. Apparently the four Keycloak security filters are present in the "originalChain" as well as in the "additionalFilters" (in contrast to Spring own security filters, which are only present in the "additionalFilters" list).