diff --git a/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/AuthoritiesExtractor.java b/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/AuthoritiesExtractor.java
index e06a07bdbba..4db5c9e9f14 100644
--- a/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/AuthoritiesExtractor.java
+++ b/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/AuthoritiesExtractor.java
@@ -22,10 +22,20 @@ import java.util.Map;
 import org.springframework.security.core.GrantedAuthority;
 
 /**
+ * Strategy used by {@link UserInfoTokenServices} to extract authorities from the resource
+ * server's response.
+ *
  * @author Dave Syer
+ * @since 1.3.0
  */
 public interface AuthoritiesExtractor {
 
+	/**
+	 * Extract the authorities from the resource server's response.
+	 *
+	 * @param map the response
+	 * @return the extracted authorities
+	 */
 	List<GrantedAuthority> extractAuthorities(Map<String, Object> map);
 
 }
diff --git a/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/FixedAuthoritiesExtractor.java b/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/FixedAuthoritiesExtractor.java
index 8a8bd85837e..3d3045fd5d5 100644
--- a/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/FixedAuthoritiesExtractor.java
+++ b/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/security/oauth2/resource/FixedAuthoritiesExtractor.java
@@ -26,7 +26,12 @@ import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 
 /**
+ * Default implementation of {@link AuthoritiesExtractor}. Extracts the authorities from
+ * the map with the key {@code authorities}. If no such value exists, a single
+ * {@code ROLE_USER} authority is returned.
+ *
  * @author Dave Syer
+ * @since 1.3.0
  */
 public class FixedAuthoritiesExtractor implements AuthoritiesExtractor {