diff --git a/config/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurer.java b/config/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurer.java
index c27cb4f2a7..27dfc8f7aa 100644
--- a/config/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurer.java
+++ b/config/src/main/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurer.java
@@ -350,11 +350,9 @@ public final class OAuth2LoginConfigurer<B extends HttpSecurityBuilder<B>>
 				oidcAuthorizationCodeAuthenticationProvider.setAuthoritiesMapper(userAuthoritiesMapper);
 				oidcAuthorizedClientRefreshedEventListener.setAuthoritiesMapper(userAuthoritiesMapper);
 			}
-			oidcAuthorizationCodeAuthenticationProvider = this.postProcess(oidcAuthorizationCodeAuthenticationProvider);
-			http.authenticationProvider(oidcAuthorizationCodeAuthenticationProvider);
+			http.authenticationProvider(this.postProcess(oidcAuthorizationCodeAuthenticationProvider));
 
-			oidcAuthorizedClientRefreshedEventListener = this.postProcess(oidcAuthorizedClientRefreshedEventListener);
-			registerDelegateApplicationListener(oidcAuthorizedClientRefreshedEventListener);
+			registerDelegateApplicationListener(this.postProcess(oidcAuthorizedClientRefreshedEventListener));
 			configureOidcUserRefreshedEventListener(http);
 		}
 		else {
diff --git a/config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurerTests.java b/config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurerTests.java
index 6428609517..cc1a30a381 100644
--- a/config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurerTests.java
+++ b/config/src/test/java/org/springframework/security/config/annotation/web/configurers/oauth2/client/OAuth2LoginConfigurerTests.java
@@ -29,6 +29,7 @@ import org.junit.jupiter.api.AfterEach;
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Mockito;
 
 import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.beans.factory.NoUniqueBeanDefinitionException;
@@ -43,11 +44,14 @@ import org.springframework.http.MediaType;
 import org.springframework.mock.web.MockFilterChain;
 import org.springframework.mock.web.MockHttpServletRequest;
 import org.springframework.mock.web.MockHttpServletResponse;
+import org.springframework.security.authentication.AuthenticationProvider;
 import org.springframework.security.authentication.event.AuthenticationSuccessEvent;
 import org.springframework.security.config.Customizer;
+import org.springframework.security.config.ObjectPostProcessor;
 import org.springframework.security.config.annotation.SecurityContextChangedListenerConfig;
 import org.springframework.security.config.annotation.web.builders.HttpSecurity;
 import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
+import org.springframework.security.config.annotation.web.configurers.oauth2.client.OAuth2LoginConfigurerTests.OAuth2LoginConfigCustomWithPostProcessor.SpyObjectPostProcessor;
 import org.springframework.security.config.oauth2.client.CommonOAuth2Provider;
 import org.springframework.security.config.test.SpringTestContext;
 import org.springframework.security.config.test.SpringTestContextExtension;
@@ -711,6 +715,22 @@ public class OAuth2LoginConfigurerTests {
 		verifyNoInteractions(clientRegistrationRepository, authorizedClientRepository);
 	}
 
+	// gh-17175
+	@Test
+	public void oauth2LoginWhenAuthenticationProviderPostProcessorThenUses() throws Exception {
+		loadConfig(OAuth2LoginConfigCustomWithPostProcessor.class);
+		// setup authorization request
+		OAuth2AuthorizationRequest authorizationRequest = createOAuth2AuthorizationRequest();
+		this.authorizationRequestRepository.saveAuthorizationRequest(authorizationRequest, this.request, this.response);
+		// setup authentication parameters
+		this.request.setParameter("code", "code123");
+		this.request.setParameter("state", authorizationRequest.getState());
+		// perform test
+		this.springSecurityFilterChain.doFilter(this.request, this.response, this.filterChain);
+		// assertions
+		verify(this.context.getBean(SpyObjectPostProcessor.class).spy).authenticate(any());
+	}
+
 	private void loadConfig(Class<?>... configs) {
 		AnnotationConfigWebApplicationContext applicationContext = new AnnotationConfigWebApplicationContext();
 		applicationContext.register(configs);
@@ -1296,6 +1316,52 @@ public class OAuth2LoginConfigurerTests {
 
 	}
 
+	@Configuration
+	@EnableWebSecurity
+	static class OAuth2LoginConfigCustomWithPostProcessor {
+
+		private final ClientRegistrationRepository clientRegistrationRepository = new InMemoryClientRegistrationRepository(
+				GOOGLE_CLIENT_REGISTRATION);
+
+		private final ObjectPostProcessor<AuthenticationProvider> postProcessor = new SpyObjectPostProcessor();
+
+		@Bean
+		SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
+			// @formatter:off
+			http
+				.oauth2Login((oauth2Login) -> oauth2Login
+					.clientRegistrationRepository(this.clientRegistrationRepository)
+					.withObjectPostProcessor(this.postProcessor)
+				);
+			// @formatter:on
+			return http.build();
+		}
+
+		@Bean
+		ObjectPostProcessor<AuthenticationProvider> mockPostProcessor() {
+			return this.postProcessor;
+		}
+
+		@Bean
+		HttpSessionOAuth2AuthorizationRequestRepository oauth2AuthorizationRequestRepository() {
+			return new HttpSessionOAuth2AuthorizationRequestRepository();
+		}
+
+		static class SpyObjectPostProcessor implements ObjectPostProcessor<AuthenticationProvider> {
+
+			AuthenticationProvider spy;
+
+			@Override
+			public <O extends AuthenticationProvider> O postProcess(O object) {
+				O spy = Mockito.spy(object);
+				this.spy = spy;
+				return spy;
+			}
+
+		}
+
+	}
+
 	private abstract static class CommonSecurityFilterChainConfig {
 
 		SecurityFilterChain configureFilterChain(HttpSecurity http) throws Exception {