Background: Organisations known as paper mills charge authors to place fraudulent papers in the academic literature. Publishers have been slow to tackle the problem, but are now starting to devise methods for identifying paper mill products. However, little attention has been paid to the topic of complicit editors, who can take over special issues of journals and then publish many fraudulent articles. To date, activities of such editors have been documented by a handful of sleuths on social media and on the website PubPeer. This paper reports a descriptive study that documents more systematically the presence of “red flags” indicative of paper mill activity in special issues from the Wiley-Hindawi Open Access publishing partnership. Methods: A spreadsheet was created from the Hindawi website with records for all published articles during 2022. Initial analysis focused on initial Editor Response Time (RT) in ten journals that had been identified by sleuths as having high rates of problematic papers. In a second step, the whole dataset was scrutinized to identify editors who had handled at least 10 articles. These were divided into those who had had at least one PubPeer comment flagging dubious content or citations, and those with no PubPeer comments.Results: A cutoff of 22 days was identified as corresponding to the 2nd percentile of Editor RT for regular articles not in special issues. Plots show that in the 10 selected journals, some special issues have 50% or more of Editor RTs below this cutoff, raising questions as to whether an appropriate peer review process had taken place. Editors with articles flagged on PubPeer processed significantly more articles and had significantly shorter Editor RT than other editors. They often acted as editors in multiple issues. Other potential red flags, i.e., proportions of papers accepted without revision, or lack of diversity of author emails did not distinguish the two subgroups of editors. Discussion: Relatively simple indicators, of number of articles processed and speed of editorial processing, can be used as red flags that suggest an editor should be investigated to ensure they are not part of a paper mill. Conclusion: To tackle paper mills, it is crucial to move from a focus on individual articles to identify and root out individuals who have used positions as guest editors of special issues to flood the literature with fraudulent material. It is hoped that this analysis makes a start in suggesting approaches that can be used to this end.