That would explain why I got an email about being attacked all over the place.

That's a documented feature, not a bug or exploit.

If a harvester has no capacity to take the harvested energy, it falls to the ground. Containers are automatically filled with resources falling on them.

Well the tutorial (Tutorial 1) says:

"Now let's improve our code by taking the workers' behavior out into a separate module. Create a module called role.harvester with the help of the Modules section on the left of the script editor and define a run function inside the module.exports object, containing the creep behavior."

And in the mentioned module section/list (which is headed by the title "MODULES"), there is a text box that says "New module name...", where you can type the module name and press enter, and you have your new module.

So I wonder, at which point did the tutorial lose you?

If you can't afford the 5% to put the subscription token, I think it's very unlikely that someone could afford your subscription token as of now.

To get the initial money, just mine all your minerals and sell them to the NPCs, except catalyst, for which there is actually some demand by the players. This should give you the credits to list your order easily.

No, you have to use market.deal. The last argument of terminal.send is not an id, but a text description.

Maybe make it that safe mode has to be activated in all rooms at the same time. This would still ensure that defenders cannot be caught on surprise, but prevents any multi-room cheese.

The attacker has then 30k ticks (~24 hours) to attack any rooms of the defender. Meaning that no matter what, the attacker can also attack in his timezone.

Also caching orders is a bad idea, as players can now change the order price. With a fast method to access an order by id, we could easily check whether the price is still the same.

Great addition! Many Screeps players will sleep much better now

You might also want to block the attackController method for completeness.

Note that if you deal with an existing order, you are not charged the 5% fee. You are charged with the transfer cost in energy, though.

So to get your initial credits, you need to deal with existing buy orders. There are NPC buy orders for all basic minerals (find one close to you by the market interface), and use these to get some credits easily.

The same happens if an invader sits on an exit tile, and your creep enters the same tile from another room.