DNS service Cloudflare has suffered a memory leak that has exposed user data for thousands (possibly millions) of websites. This page has a list of the most notable (potentially) affected domains, and a zip with all possibly affected domains. If you use any of the listed sites, it would be a very good idea to change your passwords for them. If you use the same password on any other site, it would be a very good idea to change *those* too. (it's a terrible idea to share passwords anyway)
Change your passwords.