diff --git a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/AbstractWebClientReactiveOAuth2AccessTokenResponseClient.java b/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/AbstractWebClientReactiveOAuth2AccessTokenResponseClient.java
index 68b0818ace..08027df456 100644
--- a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/AbstractWebClientReactiveOAuth2AccessTokenResponseClient.java
+++ b/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/AbstractWebClientReactiveOAuth2AccessTokenResponseClient.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,6 @@
 
 package org.springframework.security.oauth2.client.endpoint;
 
-import java.io.UnsupportedEncodingException;
-import java.net.URLEncoder;
-import java.nio.charset.StandardCharsets;
 import java.util.Collections;
 import java.util.Set;
 
@@ -100,19 +97,7 @@ public abstract class AbstractWebClientReactiveOAuth2AccessTokenResponseClient<T
 		headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
 		if (ClientAuthenticationMethod.CLIENT_SECRET_BASIC.equals(clientRegistration.getClientAuthenticationMethod())
 				|| ClientAuthenticationMethod.BASIC.equals(clientRegistration.getClientAuthenticationMethod())) {
-			String clientId = encodeClientCredential(clientRegistration.getClientId());
-			String clientSecret = encodeClientCredential(clientRegistration.getClientSecret());
-			headers.setBasicAuth(clientId, clientSecret);
-		}
-	}
-
-	private static String encodeClientCredential(String clientCredential) {
-		try {
-			return URLEncoder.encode(clientCredential, StandardCharsets.UTF_8.toString());
-		}
-		catch (UnsupportedEncodingException ex) {
-			// Will not happen since UTF-8 is a standard charset
-			throw new IllegalArgumentException(ex);
+			headers.setBasicAuth(clientRegistration.getClientId(), clientRegistration.getClientSecret());
 		}
 	}
 
diff --git a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/OAuth2AuthorizationGrantRequestEntityUtils.java b/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/OAuth2AuthorizationGrantRequestEntityUtils.java
index 91f4a597ba..e7fdce4bcb 100644
--- a/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/OAuth2AuthorizationGrantRequestEntityUtils.java
+++ b/oauth2/oauth2-client/src/main/java/org/springframework/security/oauth2/client/endpoint/OAuth2AuthorizationGrantRequestEntityUtils.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,9 +16,6 @@
 
 package org.springframework.security.oauth2.client.endpoint;
 
-import java.io.UnsupportedEncodingException;
-import java.net.URLEncoder;
-import java.nio.charset.StandardCharsets;
 import java.util.Collections;
 
 import org.springframework.core.convert.converter.Converter;
@@ -51,23 +48,11 @@ final class OAuth2AuthorizationGrantRequestEntityUtils {
 		headers.addAll(DEFAULT_TOKEN_REQUEST_HEADERS);
 		if (ClientAuthenticationMethod.CLIENT_SECRET_BASIC.equals(clientRegistration.getClientAuthenticationMethod())
 				|| ClientAuthenticationMethod.BASIC.equals(clientRegistration.getClientAuthenticationMethod())) {
-			String clientId = encodeClientCredential(clientRegistration.getClientId());
-			String clientSecret = encodeClientCredential(clientRegistration.getClientSecret());
-			headers.setBasicAuth(clientId, clientSecret);
+			headers.setBasicAuth(clientRegistration.getClientId(), clientRegistration.getClientSecret());
 		}
 		return headers;
 	}
 
-	private static String encodeClientCredential(String clientCredential) {
-		try {
-			return URLEncoder.encode(clientCredential, StandardCharsets.UTF_8.toString());
-		}
-		catch (UnsupportedEncodingException ex) {
-			// Will not happen since UTF-8 is a standard charset
-			throw new IllegalArgumentException(ex);
-		}
-	}
-
 	private static HttpHeaders getDefaultTokenRequestHeaders() {
 		HttpHeaders headers = new HttpHeaders();
 		headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON_UTF8));
diff --git a/oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/endpoint/OAuth2ClientCredentialsGrantRequestEntityConverterTests.java b/oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/endpoint/OAuth2ClientCredentialsGrantRequestEntityConverterTests.java
index 1420135b8b..b509cfcd35 100644
--- a/oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/endpoint/OAuth2ClientCredentialsGrantRequestEntityConverterTests.java
+++ b/oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/endpoint/OAuth2ClientCredentialsGrantRequestEntityConverterTests.java
@@ -16,11 +16,6 @@
 
 package org.springframework.security.oauth2.client.endpoint;
 
-import java.io.UnsupportedEncodingException;
-import java.net.URLEncoder;
-import java.nio.charset.StandardCharsets;
-import java.util.Base64;
-
 import org.junit.Before;
 import org.junit.Test;
 import org.mockito.InOrder;
@@ -133,37 +128,4 @@ public class OAuth2ClientCredentialsGrantRequestEntityConverterTests {
 		assertThat(formParameters.getFirst(OAuth2ParameterNames.SCOPE)).contains(clientRegistration.getScopes());
 	}
 
-	// gh-9610
-	@SuppressWarnings("unchecked")
-	@Test
-	public void convertWhenSpecialCharactersThenConvertsWithEncodedClientCredentials()
-			throws UnsupportedEncodingException {
-		String clientCredentialWithAnsiKeyboardSpecialCharacters = "~!@#$%^&*()_+{}|:\"<>?`-=[]\\;',./ ";
-		// @formatter:off
-		ClientRegistration clientRegistration = TestClientRegistrations.clientCredentials()
-				.clientId(clientCredentialWithAnsiKeyboardSpecialCharacters)
-				.clientSecret(clientCredentialWithAnsiKeyboardSpecialCharacters)
-				.build();
-		// @formatter:on
-		OAuth2ClientCredentialsGrantRequest clientCredentialsGrantRequest = new OAuth2ClientCredentialsGrantRequest(
-				clientRegistration);
-		RequestEntity<?> requestEntity = this.converter.convert(clientCredentialsGrantRequest);
-		assertThat(requestEntity.getMethod()).isEqualTo(HttpMethod.POST);
-		assertThat(requestEntity.getUrl().toASCIIString())
-				.isEqualTo(clientRegistration.getProviderDetails().getTokenUri());
-		HttpHeaders headers = requestEntity.getHeaders();
-		assertThat(headers.getAccept()).contains(MediaType.APPLICATION_JSON_UTF8);
-		assertThat(headers.getContentType())
-				.isEqualTo(MediaType.valueOf(MediaType.APPLICATION_FORM_URLENCODED_VALUE + ";charset=UTF-8"));
-		String urlEncodedClientCredential = URLEncoder.encode(clientCredentialWithAnsiKeyboardSpecialCharacters,
-				StandardCharsets.UTF_8.toString());
-		String clientCredentials = Base64.getEncoder().encodeToString(
-				(urlEncodedClientCredential + ":" + urlEncodedClientCredential).getBytes(StandardCharsets.UTF_8));
-		assertThat(headers.getFirst(HttpHeaders.AUTHORIZATION)).isEqualTo("Basic " + clientCredentials);
-		MultiValueMap<String, String> formParameters = (MultiValueMap<String, String>) requestEntity.getBody();
-		assertThat(formParameters.getFirst(OAuth2ParameterNames.GRANT_TYPE))
-				.isEqualTo(AuthorizationGrantType.CLIENT_CREDENTIALS.getValue());
-		assertThat(formParameters.getFirst(OAuth2ParameterNames.SCOPE)).contains(clientRegistration.getScopes());
-	}
-
 }
diff --git a/oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/endpoint/WebClientReactiveClientCredentialsTokenResponseClientTests.java b/oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/endpoint/WebClientReactiveClientCredentialsTokenResponseClientTests.java
index ca3cadfabe..b3be304a3f 100644
--- a/oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/endpoint/WebClientReactiveClientCredentialsTokenResponseClientTests.java
+++ b/oauth2/oauth2-client/src/test/java/org/springframework/security/oauth2/client/endpoint/WebClientReactiveClientCredentialsTokenResponseClientTests.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -16,10 +16,6 @@
 
 package org.springframework.security.oauth2.client.endpoint;
 
-import java.net.URLEncoder;
-import java.nio.charset.StandardCharsets;
-import java.util.Base64;
-
 import okhttp3.mockwebserver.MockResponse;
 import okhttp3.mockwebserver.MockWebServer;
 import okhttp3.mockwebserver.RecordedRequest;
@@ -93,35 +89,6 @@ public class WebClientReactiveClientCredentialsTokenResponseClientTests {
 		assertThat(body).isEqualTo("grant_type=client_credentials&scope=read%3Auser");
 	}
 
-	// gh-9610
-	@Test
-	public void getTokenResponseWhenSpecialCharactersThenSuccessWithEncodedClientCredentials() throws Exception {
-		// @formatter:off
-		enqueueJson("{\n"
-			+ "  \"access_token\":\"MTQ0NjJkZmQ5OTM2NDE1ZTZjNGZmZjI3\",\n"
-			+ "  \"token_type\":\"bearer\",\n"
-			+ "  \"expires_in\":3600,\n"
-			+ "  \"refresh_token\":\"IwOGYzYTlmM2YxOTQ5MGE3YmNmMDFkNTVk\",\n"
-			+ "  \"scope\":\"create\"\n"
-			+ "}");
-		// @formatter:on
-		String clientCredentialWithAnsiKeyboardSpecialCharacters = "~!@#$%^&*()_+{}|:\"<>?`-=[]\\;',./ ";
-		OAuth2ClientCredentialsGrantRequest request = new OAuth2ClientCredentialsGrantRequest(
-				this.clientRegistration.clientId(clientCredentialWithAnsiKeyboardSpecialCharacters)
-						.clientSecret(clientCredentialWithAnsiKeyboardSpecialCharacters).build());
-		OAuth2AccessTokenResponse response = this.client.getTokenResponse(request).block();
-		RecordedRequest actualRequest = this.server.takeRequest();
-		String body = actualRequest.getBody().readUtf8();
-		assertThat(response.getAccessToken()).isNotNull();
-		String urlEncodedClientCredentialecret = URLEncoder.encode(clientCredentialWithAnsiKeyboardSpecialCharacters,
-				StandardCharsets.UTF_8.toString());
-		String clientCredentials = Base64.getEncoder()
-				.encodeToString((urlEncodedClientCredentialecret + ":" + urlEncodedClientCredentialecret)
-						.getBytes(StandardCharsets.UTF_8));
-		assertThat(actualRequest.getHeader(HttpHeaders.AUTHORIZATION)).isEqualTo("Basic " + clientCredentials);
-		assertThat(body).isEqualTo("grant_type=client_credentials&scope=read%3Auser");
-	}
-
 	@Test
 	public void getTokenResponseWhenPostThenSuccess() throws Exception {
 		ClientRegistration registration = this.clientRegistration