Facebook uses it to power the company blog. You can read it here.
The content on the blog dates back to 2006, but the Newsroom domain has only been around since 2012, and Facebook started using WordPress in early 2014. Before then, the Facebook blog looked just like Facebook.
The blog covers just about every change Facebook has made to the News Feed, the hows and whys of the various product launches and changes, as well as keeping readers up to date with what’s going on inside the company.
Alongside the blog, there’s company info, products, and a directory section featuring some interesting Facebook pages.
I reckon anyone who’s used WordPress for a little while would know straight away it’s powered by WordPress – the content sidebar layout gives the game away.