About a year ago I received a request to review a paper from author X in journal A. The paper uses a hype tool T to solve a common problem, which is good, but due to some shortcomings in the implementation I recommended to revise the manuscript. The editor followed my recommendation.
About a month ago I was contacted by an editor in journal B asking me to review a manuscript from unrelated authors Y. They use the same hype tool T to solve the same problem. I accepted to review it, and mentioned that I had reviewed a similar paper for a different journal (without naming it). It is now due in a couple of days.
Now to my surprise I just received a request to review a revised manuscript of author X from journal A (I thought X had given up on it since more than a year passed). I would like to accept but won't be able to deliver the review before 3-4 weeks.
This is a "winner gets it all" kind of situation. The paper that gets published first wins, and I think would be ground to drop and reject the second paper as not really novel any longer. (No plagiarism here, and nothing unethical done by the authors; just an obvious answer to an old question with hype tool T. I had myself thought of it before hearing from A, and discarded it only due to lack of time.) How should I deal with that?
Should I disclose to the respective editors that I am reviewing similar papers? I suspect that would be a breach of the confidentiality. Should I have refrained to mention to editor of journal B that I had reviewed a similar paper in the past?
Would it be a conflict of interest to review the revised manuscript from X? Should I decline the review?
Also, should I inform the editor of the other journal once the first paper gets published? If so, how can I politely ask to be informed when the manuscript gets published without giving away that there is a similar manuscript out there?
This exact situation is difficult to assess without detailed knowledge but the editors of the journals should be aware of the situation. Since each case is unique and we do not know the details it will be up to the editors to judge or take the matter further.
The Committee on Publication Ethics (COPE) has one case on simultaneous publications that can be of interst to read.
So the advice is: yes contact the editors and provide the information you can. They will then have to take action, compare manuscripts or whatever the deem necessary. Similar works have been published simultaneously before so it is not certain there is a violation lurking somewhere but it is unusual.