It might help to know what broke. Any word on what the problem was?
Someone posted something about an exploit and the next day the Foundry was taken down. I have a hard time figuring out what the exploit could be, since it seems like the Foundry missions are still up (or am I wrong about that, I haven't logged into the game to check?). You'd think if there were some exploit that normal characters could use they'd have pulled all the missions. And as far as an exploit for a Foundry character...well, who really cares?
I think it may have to do with some interesting ways to make unlimited re-spawning NPCs. I saw some interesting comments somewhere, but can't find them now. So, if it was a way to make missions where someone could unlimitedly create spawning groups they cut off the foundry access early so more people couldn't stumble into it and create missions for ill gains.
But this is just random guessing. I agree that it's probably due to the exploit bug that someone found and I doubt it has to do with Foundry characters specifically if that is the case.