Please can you tell me where did you spotted these links?
I have searched all the files and in the db and I can’t find any reference to such links.

Are you sure that the links are from May 2017 and not May 2016. I had some problems EXACTLY a year ago with this kind of links and removed them and recovered just the bare text from the former blog. Since then i had no problems with them and also if the links where from 2017 they must be with https not http like i had last year.