Author X is concerned with similarities or parallels between his manuscript, rejected in 2008, and a recently published article. "I have looked over our file and contacted the associate editor who handled the manuscript." One of the authors of the published article, author Y, was in fact a reviewer of the manuscript by author X and recommended rejection, as did two other reviewers. In the opinion of the associate editor, there are clear parallels between the article by author Y and the manuscript by author X, but these seem to be the result of common research interests rather than appropriation of ideas or data. "At this point, it is my view that author Y should have declared a conflict of interest in the review of the manuscript but has not appropriated ideas or data." – said the journal's editor.

COPE's advice was as follows: "This was a case of reviewer misconduct. The editor should contact author X and ask him to provide as much evidence as possible and then the editor can assess the situation. Ask author X if he wishes to make a more formal complaint.

More: https://publicationethics.org/guidance/case/parallels-between-unpublished-manuscript-and-published-article-other-authors