I am currently an undergraduate student and I am applying for research Masters/PhD in the US. I joined a research group before to help out on a part of a project. My coworker in this group, a PhD student has published a paper afterwards, which is irrelevant to the work that I have done, but since I have worked in his group, I was added to the co-author in his paper. I did not ask for it, but anyway, I have the publication, and I have to mention it in my application.

My fear is that, if, during the interview, I was asked about the publication, should I just say that I did not contribute to it? I do not want to lie anyway, but would that hurt my previous research group since they have added irrelevant people to the paper?

I do not think it is uncommon to have a coauthor that is not relevant to a project in my country. However, I am a bit afraid if they would take it seriously in the US.