Widely reported in the tech media, but well handled and addressed by the company itself, the scope of the recent Cloudflare data leak is somewhat staggering, as the service is so widely used.
A Github page is currently tracking sites affected by the issue, and there's some big names on the list. In fact the list is so long, we recommend changing your passwords on most important sites, and, if not already configured, taking this as an opportunity to setup a password manager and multi-factor authentication. All of the major services support this now, and Microsoft and Google both have great apps to simplify the process.
We recommend Dashlane and LastPass password managers, and a quick browser search will find detailed information on how to setup two-factor/multi-factor authentication at all the major sites.