Apparently "Guest123!" isn't the most secure password on the Internet. Who knew? If you are guilty of using common passwords, or the same password for various websites, you should consider enhancing your online security. Google's Security Checkup function now alerts users to when websites for which it stores a password have been compromised. The alert not only urges users to change the password for that particular site, but also might nudge people to not use the same password across multiple websites.