diff --git a/src/Authorization/AuthorizationDataMuxer.php b/src/Authorization/AuthorizationDataMuxer.php
index 3cf2865d70dd4536c805b65f17935477524b87b0..ce6aed51a7859a4348b945903fa7fa48bc4d589b 100644
--- a/src/Authorization/AuthorizationDataMuxer.php
+++ b/src/Authorization/AuthorizationDataMuxer.php
@@ -112,7 +112,6 @@ class AuthorizationDataMuxer
             throw new AuthorizationException(sprintf('attribute \'%s\' undefined', $attributeName), AuthorizationException::ATTRIBUTE_UNDEFINED);
         }
 
-        $wasFound = false;
         $value = $defaultValue;
         foreach ($this->authorizationDataProviders as $authorizationDataProvider) {
             $availableAttributes = $this->getProviderAvailableAttributes($authorizationDataProvider);
@@ -130,7 +129,7 @@ class AuthorizationDataMuxer
         $event = new GetAttributeEvent($this, $attributeName, $value, $userIdentifier);
         $event->setAttributeValue($value);
 
-        // Avoid endless recursions by only emitting an event for each attribtue only once
+        // Avoid endless recursions by only emitting an event for each attribute only once
         if (!in_array($attributeName, $this->attributeStack, true)) {
             array_push($this->attributeStack, $attributeName);
             $this->eventDispatcher->dispatch($event);
diff --git a/src/Authorization/EventSubscriber/AbstractGetAttributeSubscriber.php b/src/Authorization/EventSubscriber/AbstractGetAttributeSubscriber.php
index 2b30bd60e7b28834e4fbef93f22ff247f9472099..bb02caf1270b0198d71a9037ca5716dfd03a3ace 100644
--- a/src/Authorization/EventSubscriber/AbstractGetAttributeSubscriber.php
+++ b/src/Authorization/EventSubscriber/AbstractGetAttributeSubscriber.php
@@ -23,18 +23,19 @@ abstract class AbstractGetAttributeSubscriber implements EventSubscriberInterfac
 
     public function onGetAvailableAttributes(GetAvailableAttributesEvent $event)
     {
-        $event->addAttributes($this->getAvailableAttributes());
+        $event->addAttributes($this->getNewAttributes());
     }
 
     public function onGetAttributeEvent(GetAttributeEvent $event)
     {
         try {
             $this->event = $event;
-
             $attributeName = $event->getAttributeName();
-            if (in_array($attributeName, $this->getAvailableAttributes(), true)) {
-                $event->setAttributeValue($this->getUserAttributeValue($event->getUserIdentifier(), $attributeName, $event->getAttributeValue()));
-            }
+
+            $event->setAttributeValue(in_array($attributeName, $this->getNewAttributes(), true) ?
+                $this->getNewAttributeValue($event->getUserIdentifier(), $attributeName, $event->getAttributeValue()) :
+                $this->updateExistingAttributeValue($event->getUserIdentifier(), $attributeName, $event->getAttributeValue())
+            );
         } finally {
             $this->event = null;
         }
@@ -50,15 +51,25 @@ abstract class AbstractGetAttributeSubscriber implements EventSubscriberInterfac
         return $this->event->getAttribute($attributeName, $defaultValue);
     }
 
+    /**
+     * @param mixed|null $attributeValue The current attribute value
+     *
+     * @return mixed|null The updated attribute value
+     */
+    protected function updateExistingAttributeValue(?string $userIdentifier, string $attributeName, $attributeValue)
+    {
+        return $attributeValue;
+    }
+
     /*
-     * @return string[]
+     * @return string[] The array of new attribute names that this subscriber provides
      */
-    abstract protected function getAvailableAttributes(): array;
+    abstract protected function getNewAttributes(): array;
 
     /**
-     * @param mixed|null $attributeValue
+     * @param mixed|null $defaultValue the default value if provided explicitly in the authorization expression, else null
      *
-     * @return mixed|null
+     * @return mixed|null the value for the new attribute with the given name for the given user
      */
-    abstract protected function getUserAttributeValue(?string $userIdentifier, string $attributeName, $attributeValue);
+    abstract protected function getNewAttributeValue(?string $userIdentifier, string $attributeName, $defaultValue);
 }