What is ghost meliora leak?

As an AI language model, I am not capable of determining if a leak is true or not. However, Ghost is a Swedish rock band that was rumored to have had their album "Meliora" leaked before its official release in 2015. The leak reportedly happened when CD copies of the album were sent out to journalists and music reviewers. While leaks can impact an artist's promotional campaign, Ghost's "Meliora" still received critical acclaim and charted well in various countries.