I received an email:
I write this letter on behalf of authors seeking to co-publish. We have seen your previous works and they were considered to be of high quality. Therefore, I offer you a co-publishing partnership. Our clients wish to buy positions in scientific articles that are in line with their research interests. As our partner, you can offer us a position or two in your work.
How should I respond to this request to bribe me? Is it permitted to sell coauthorships?