TLDR: If you have an iThemes account (for “Backup Buddy,” “SecurityPro,” or their other plugins or themes), change your password now. If you use those same credentials at other sites, change those passwords now as well.
Five million Gmail (and therefore Google Account!) passwords were stolen and posted online yesterday.
Use the site haveibeenpwned.com to check your passwords against this and other major breeches.
This is a great time to update your password and enable two-factor authentication.
Also, if you don’t already do it, start using a password management system. I like using Keepass with DropBox (aff. link), but the most important thing is to start using long (like more than 17 characters!) passwords.