I'm not sure if this is really a bug or what's going on but I have 250 CSC that I definitely did not buy. I am aware that a little while ago everyone was given CSC as the result of downtime or problems with Subeta or something. I don't remember the reason but I am 99% sure I already used them as soon as I got them. But now I have 250 CSC and I haven't bought any recently and I was just wondering where this came from. I did have a bunch of trades up but they were all "free" trades and unless someone offered CSC and I just did not notice then I really have no idea where this came from.
Staff gave us 250 CSC (as stated in this newspost) but I'd suggest you to file a ticket and have a User Admin to help you. Also, you can check this page to see your purchase history.