joomla/joomla-cms — comment on commit d6f5311239e7ea211c54da77aca33602ebcd441f
File: administrator/components/com_menus/models/item.php line 102
By mbabker:

It's used in batchAccess, batchLanguage, and batchMove. The intent is to improve the ACL checks by checking the appropriate asset versus the component level permissions. Neither batchCopy or batchMove use this array to check create permissions since that check is being performed on the new parent asset. In core use, the contexts array is not used in batchCopy since no edit checks are done, but theoretically, it could be used by 3PD.