Because of the sensational headline, I'm not even going to click on this. Is there even a real difference between The Guardian and the Daily Mail?
It has examples of the campaigns of national political parties of different nations (hence world leaders) using a loophole that facebook pages can do certain things facebook accounts can't to boost their engagement and/or avoid the scrutiny an account would get.
It also has a really good non-techy breakdown explaining how it works. I think it's HTML5? Having read it, I would say it's a really good piece of journalism.
Detailing how it works and as well as how slow facebook are to respond.
What is sensational about that? Unless you dislike reporting of propaganda efforts by governments.