This is one of the reasons we have turned off sending for now. We noticed this as well, and are trying to figure out what happened exactly.. For now we are suspecting someone used our first API to do this. We kept it around for some compatibilty issues, but it's deprecated now. The new API is MUCH more improved. We don't want to restore sending until we are 100% sure this won't happen again.
Glad to hear you noticed and are on it

having bought MCZ last month at the higher price, and continuing to buy as it dropped it was a bit of shock to see the supply shoot up like that.
We are really sorry for what happened, those users will be banned. We are all over it