I had an older WP site get hacked and ive been tracking it down, pretty insane amount of work these scripts go though, but if you want to see an entry point I made a script to log all post events, im actually running this along with wordfence now and its very interesting the amount of base64 attacks you see attempted on themes, plugins ext..
if you want to see try this, beware though if you actually authenticate (log in) it will record your login in the log and you do not want that info out there so be sure to delete it if you do.. I added a mylogin you can exclude name but password will still appear!
Place this at the top of config file and create mylogfile.txt file in same directory
Code:
$mylogin ="Your Username";
$date = date('m/d/Y h:i:s a', time());
$filename = "mylogfile.txt";
$actual_link = "http://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";
$text = "";
if ($_POST){
foreach($_POST as $key => $value)
{
if ($value != $mylogin){
$text .= "\n post - ".$date ."\n".$actual_link."\n".$key." : ".$value."\n";
}
}
file_put_contents($filename, $text, FILE_APPEND | LOCK_EX) ;
}