Fix #260 - tightening up the is_ajax_request() method in the Input class.  Thanks sophistry for the suggestion
diff --git a/system/core/Input.php b/system/core/Input.php
index 6f88b19..9d8811c 100644
--- a/system/core/Input.php
+++ b/system/core/Input.php
@@ -635,8 +635,7 @@
 	 */
 	public function is_ajax_request()
 	{
-		$req_source = $this->server('HTTP_X_REQUESTED_WITH');
-		return ($req_source == 'XMLHttpRequest') ? TRUE : FALSE;
+		return ($this->server('HTTP_X_REQUESTED_WITH') === 'XMLHttpRequest');
 	}
 
 }