The TLDR is this old man hid about $1 Million Dollars worth of Gold and Jewels somewhere in the United States about 10 years ago. He gave poem clues in a book and thousands have tried looking for this treasure. Few have died also unfortunately.
Fenn did not say who or where the treasure was found, but does confirm it was found.
Here is the full story:
https://www.santafenewmexican.com/news/local_news/forrest-fenn-confirms-his-treasure-has-been-found/article_37006cfe-a8d7-11ea-8653-873ca96e31ef.html