How Long is Confidentiality Required in Hiring Process?

Got a tentative offer for a new position. And before I could tell my supervisor (they knew I had interviewed) someone from upper management told a staff member who then told my supervisor (literally the next day after I was given the tentative offer).

This pissed me off. I alway try to keep every step of the hiring process confidential until I get that official offer. And if it's internal I ASK if they want me to announce it or do they want to.

It especially pissed me off because we got emails about manager needing to keep things confidential from the same upper manager that told the staff member about my tentative offer. And we had no clue if HR was going to approve it or not (we've been having freezes).

Am I wrong in thinking that confidentially should be kept until at least the official offer comes in?