I have a small AJAX application, written in PHP that I did not secure from the start. I would like some recommendations on how to now secure the app, things to implement and check for. I have not found any exhaustive guides on google, and hope that some can be recommended.
It is a small application that connects to and displays records from a mysql database. It is not using any external libraries.
I am unsure about how to protect on passing in variables, such as:
if (isset($_GET['cmd'])) $cmd = $_GET['cmd'];
Should I simply declare $cmd to something before check isset?
If you are talking about securing the app (as opposed to the server/ environment it is on – which I am not really qualified to address) then I would consider the following: