A customer accidently posted a message on a project managing website that was quickly deleted from view because it was meant to be an internal reply to the customer's team. However, when a comment is posted on this site the messages are emailed out to everyone in the project, including me, regardless if the message on the website are deleted later. My boss gets 40 of these emails every day and does not go through them like I do which was when I found the deleted message.
Should I tell my boss about the negative comment the customer posted? What's the ethical thing to do here? Bringing it up may harm the contract between us and customer, but it may also go a different direction.