A Florida defendant forwards an email (not an accident) to a plaintiff that contains discussion between defendant's attorney and said defendant. Is the forwarded forwarded client-attorney privileged?
Voluntary disclosure, even accidental, by the client ends privilege.
The information may still be confidential (inadmissible) if it happened in the appropriate circumstances, for example, as part of a mediation.
A recent decision of the High Court of Australia has determined that a litigant can use material that comes into its possession that would have attracted privilege irrespective of how this happens. In that case, the law firm was hacked by an unknown party, the information was given to a journalist and published and the litigant wanted to use it in their case - they were allowed to do so. The court decided that privilege is not a legal right that could found a course of action. Basically, it only prevents the compulsory production of such information - it doesn't protect the information itself.