Hi Xb95, we first removed the heroku add-on and thought that it would automatically destroy the database, but that turned out not to be the case. So what we did to fix the issue was purge all of the tables from the database. Now the credentials still work, but they reach an empty database without any content. We're working on revoking the access token for all affected users right now. Thanks for helping us through this.
I'm not sure how to validate that this is still timely, though... oh, I created a table:
public | hacker_news_1342216769 | table | ruwdncbzdkulsh
With the current timestamp. So, if you changed anything, it hasn't actually taken effect in the part that matters -- the exposed database.