I found this information regarding private conversations & confessions within the church from an Anglican point of view, and it relates not only to the clergy but anyone in the church eg cleaners, congregation etc. I am not sure if this also applies to the Catholic church...
''There are times when some information comes to you that cannot be kept entirely to yourself. It may be that the person involved is in a situation that affects others, has committed a crime, or is in personal danger. It would be irresponsible to keep such information to yourself.
In the first instance you must be honest with the person who is giving you the information; tell them of your concerns and of the need to pass on the information. Ask for their permission so to do, explaining that it would be in their own interests for this to be done. Tell them with whom you intend to share the information and what you think will be the likely consequences. If the person giving the information is adamant that it may not be shared it is vital to seek further advice. Go to someone whom you trust and tell them of your dilemma � remembering always that you must not divulge the actual information, just that you are in a difficult situation. It may be that your adviser is able to suggest a way forward but remember, it is still your challenge.
If all else fails and you find yourself party to some information which you cannot keep to yourself you should meet again with the person who gave you the information and tell them, straightforwardly, what you intend to do. This may cause some distress, you may be accused of breaking a confidential relationship, but you must stand firm in the interests of other people.''