WordPress, a procedural set of scripts half acting like object orientated code that when you do poke around under the hood you will quickly become lost. Try follow the documentation to attempt to build anything other than a blog and you will hit wall after wall after wall. The naming conventions, the structure is extremely sub par.
Get a pluggin. Great… but the chances are that the coding style, documentation etc etc are at a sub par standard.
There are so many sites out there built with wordpress, it’s crazy!
WordPress is shit for anything other than a std blog. If you need to start selling anything, applying any real user roles and policies, want to do anything other than use pluggins out of the box… look for something else. There are a whole load of alternatives that will give you the freedom to create something much more modern and secure.
/xmlrpc.php for a starters… and that is core of flipping wordpress right there!
Seriously, save yourself the agro. WordPress is where you go when you don’t want to write any code and only want to write a blog.