diff --git a/config/src/main/java/org/springframework/security/config/annotation/web/configurers/WebAuthnConfigurer.java b/config/src/main/java/org/springframework/security/config/annotation/web/configurers/WebAuthnConfigurer.java
index 90bf29ae45..e589959209 100644
--- a/config/src/main/java/org/springframework/security/config/annotation/web/configurers/WebAuthnConfigurer.java
+++ b/config/src/main/java/org/springframework/security/config/annotation/web/configurers/WebAuthnConfigurer.java
@@ -177,6 +177,7 @@ public class WebAuthnConfigurer<H extends HttpSecurityBuilder<H>>
 		WebAuthnAuthenticationFilter webAuthnAuthnFilter = new WebAuthnAuthenticationFilter();
 		webAuthnAuthnFilter.setAuthenticationManager(
 				new ProviderManager(new WebAuthnAuthenticationProvider(rpOperations, userDetailsService)));
+		webAuthnAuthnFilter = postProcess(webAuthnAuthnFilter);
 		WebAuthnRegistrationFilter webAuthnRegistrationFilter = new WebAuthnRegistrationFilter(userCredentials,
 				rpOperations);
 		PublicKeyCredentialCreationOptionsFilter creationOptionsFilter = new PublicKeyCredentialCreationOptionsFilter(
diff --git a/config/src/test/java/org/springframework/security/config/annotation/web/configurers/WebAuthnConfigurerTests.java b/config/src/test/java/org/springframework/security/config/annotation/web/configurers/WebAuthnConfigurerTests.java
index d8465e4e27..60674ab4ba 100644
--- a/config/src/test/java/org/springframework/security/config/annotation/web/configurers/WebAuthnConfigurerTests.java
+++ b/config/src/test/java/org/springframework/security/config/annotation/web/configurers/WebAuthnConfigurerTests.java
@@ -23,6 +23,7 @@ import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
 
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.config.BeanPostProcessor;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.http.HttpOutputMessage;
@@ -42,6 +43,7 @@ import org.springframework.security.web.SecurityFilterChain;
 import org.springframework.security.web.authentication.ui.DefaultResourcesFilter;
 import org.springframework.security.web.webauthn.api.PublicKeyCredentialCreationOptions;
 import org.springframework.security.web.webauthn.api.TestPublicKeyCredentialCreationOptions;
+import org.springframework.security.web.webauthn.authentication.WebAuthnAuthenticationFilter;
 import org.springframework.security.web.webauthn.management.WebAuthnRelyingPartyOperations;
 import org.springframework.security.web.webauthn.registration.HttpSessionPublicKeyCredentialCreationOptionsRepository;
 import org.springframework.test.web.servlet.MockMvc;
@@ -88,6 +90,14 @@ public class WebAuthnConfigurerTests {
 			.andExpect(content().string(containsString("body {")));
 	}
 
+	// gh-18128
+	@Test
+	public void webAuthnAuthenticationFilterIsPostProcessed() throws Exception {
+		this.spring.register(DefaultWebauthnConfiguration.class, PostProcessorConfiguration.class).autowire();
+		PostProcessorConfiguration postProcess = this.spring.getContext().getBean(PostProcessorConfiguration.class);
+		assertThat(postProcess.webauthnFilter).isNotNull();
+	}
+
 	@Test
 	public void webauthnWhenNoFormLoginAndDefaultRegistrationPageConfiguredThenServesJavascript() throws Exception {
 		this.spring.register(NoFormLoginAndDefaultRegistrationPageConfiguration.class).autowire();
@@ -289,6 +299,26 @@ public class WebAuthnConfigurerTests {
 
 	}
 
+	@Configuration(proxyBeanMethods = false)
+	static class PostProcessorConfiguration {
+
+		WebAuthnAuthenticationFilter webauthnFilter;
+
+		@Bean
+		BeanPostProcessor beanPostProcessor() {
+			return new BeanPostProcessor() {
+				@Override
+				public Object postProcessAfterInitialization(Object bean, String beanName) {
+					if (bean instanceof WebAuthnAuthenticationFilter filter) {
+						PostProcessorConfiguration.this.webauthnFilter = filter;
+					}
+					return bean;
+				}
+			};
+		}
+
+	}
+
 	@Configuration
 	@EnableWebSecurity
 	static class DefaultWebauthnConfiguration {