It was quite amazing what people would submit unprompted, so I'm not at all surprised that people would feed sensitive data into ChatGPT. The next cycle will be that ChatGPT gets - surprise - trained on that data, and may start using fragments of it - which may well still be sensitive enough to cause trouble - as its output.
Don't paste confidential information into a textbox, in fact don't trust anybody or any company with your confidential information unless there is a strong contractual relationship backed up by penalties if it gets broken. And even then: the ultimate responsibility is yours, you may be able to recover some $ for damages but your reputation may well be toast.