[Security] fixed a leak in ExceptionListener

src/Symfony/Component/Security/Http/Firewall/ExceptionListener.php

@@ -76,6 +76,10 @@ class ExceptionListener
      */
     public function onKernelException(GetResponseForExceptionEvent $event)
     {
+        // we need to remove ourselves as the exception listener can be
+        // different depending on the Request
+        $event->getDispatcher()->removeListener(KernelEvents::EXCEPTION, array($this, 'onKernelException'));
+
         $exception = $event->getException();
         $request = $event->getRequest();