Years ago before social media was huge it was common for people to join blog sites to engage with like-minded or oppositely-minded people. With zero expectation of anyone joining my little blog I checked a box that allowed anyone to register as a user. Within a few minutes a user registered with an email address ending in .ru. I had imagined I would get a few non-person users but not that fast.
WordPress has been hit pretty hard over the last few weeks with a number of exploits discovered. I very quickly disabled that feature that lets anyone register and don’t believe any harm was done.