Adding configuration item to set what valid characters are for the image

filename.

webroot/img_config.php

@@ -17,6 +17,13 @@ return array(
 
 
 
+    /**
+     * Check image filename that it only contain valid characters.
+     */
+    'valid_filename' => '#^[a-z0-9A-Z-/_\.]+$#',
+
+
+
     /**
      * Set default timezone, it defaults to UTC if not specified otherwise.
      *