Hell, PiNG had'nt even been released for a few hours and I had a few people sending me messages containing 'secure' server information (such as database locations..). -< which could have only been obtained via breaking into the game.
In a server-client model, you need to consider how much control the client has over the game. There is a lot of literature on this topic given that online gaming is big business and people have real concerns when it comes to cheaters in competitive games.
On one extreme, you can have a very trustworthy server that just accepts whatever a client sends and assumes it's honest data. This is how a transaction might look
On the other extreme, you have a server that does not trust the client at all. The client can only send instructions from the player, and the server will determine whether it'll listen to you or not.
You have a lot more work to do in a server-client game, because there are plenty of trade-offs depending on how much control you want to give the client. In a completely server-sided game, where the client's only job is to render the results of your actions, the only way that someone could cheat in your game is to hack your server directly. This obviously is very restrictive and may have huge performance implications (primarily network latency).
Now, if you are aware that RPG Maker data can be easily obtained, why are you putting your "secure" communication methods inside the scripts, where it is easily obtained?