Can a bank discuss your loan with anyone without your permission?

They are usually not allowed to. There are confidentiality clauses in most bank loans, and generally, information about your financial status may not be revealed to other family members or journalists or nosy neighbors (or whoever) without your permission. If you sign a waiver, you could give another person, like a spouse, permission to know about the loan; and if the spouse or family member is a co-signer, they would of course know about it. But strangers or people to whom you did not give permission would usually not be given any of your confidential information.

However, it should be noted that banks do report to credit bureaus, and if you are delinquent in your payments, that information would become part of your credit history; other agencies could access it to learn more about you when you apply for credit at some future time.