This error shows up in the error log after upgrading MODX:
[2018-11-30 19:40:14] (ERROR in modMenu::getSubMenus @ /www/htdocs/modx/core/model/modx/modmenu.class.php : 145) modAction support is deprecated since version 2.3.0. Support for modAction has been replaced with routing based on a namespace and action name. Please update the extra with the namespace fileattach to the routing based system.
This error shows up in the error log after upgrading MODX: