Google has sent out security alerts to WordPress site owners, telling them their website was running an out of date version. Many webmasters running up-to-date versions received the alerts, when it was clear they shouldn’t have. Google was sending these messages as a courtesy in case website owners forgot to update their sites, not as an official warning. Google has been sending these alerts since 2009, and has been targeting site owners who deploy popular CMS platforms such as WordPress, Joomla, or Drupal.
Source: https://www.bleepingcomputer.com/news/security/google-makes-wordpress-site-owners-nervous-due-to-confusing-security-alerts/