A book is published containing cited text from an article licensed under some free license like CC-BY-SA. With all requirements of such license fulfilled.
Later on the "author" of the article confesses that it was not original work and did not in fact have the right to grant licenses for the article.
What are the responsabilities of the book's author and publisher?
Is it a copyright infringement to continue publishing it unmodified claiming that any damage is caused by the author of the article and not the book's author whom acted in good faith?
Otherwise, is it a copyright infringement to reject acting on such revelation until proof is provided about the illegality of the cited article? If the author choses to keep the cited text, is there any obligation to actively investigate the license status?
Note that there is no doubt that the identities of the article's author and the one claiming it was a false license are the same. There is doubt about the veracity of his words though since he must have lied at least once, when he falsely granted a license or when he falsely confessed.