Press the Allow button to verify you are human

I've just started getting this weird page coming up when I access a book record. It asks me whether I am human and wants me to click a button. I'm very reluctant to do that. Is this something LibraryThing has instituted or am I the victim of some sort of malware? If it's the former, some sort of notice would have been appreciated.

>1 dajashby: The website is currently being attacked by spammers. Do not click on anything that has directed you outside of LT. Details here: https://www.librarything.com/topic/363323

Thanks for the prompt response. Good to know my instincts are still up to scratch...