I found this, it seems that data is now missing:
jQuery.post( url [, data] [, success(data, textStatus, jqXHR)] [, dataType] )
urlA string containing the URL to which the request is sent.
dataA map or string that is sent to the server with the request.
success(data, textStatus, jqXHR)A callback function that is executed if the request succeeds.
dataTypeThe type of data expected from the server. Default: Intelligent Guess (xml, json, script, text, html).