Windows 10 version 1703, otherwise known as the Creators Update, has now reached end of service and will no longer receive any future security or quality updates. Users running consumer, enterprise, and education versions of Windows 10 1703 are required to upgrade to Windows 10 1903 in order to continue receiving updates. The consumer version 1803 is the next version to go out of service on November 12th, 2019, with the enterprise version going EoS in November 2020. New vulnerabilities come out every month that can be utilized by phishing campaigns, malicious web sites, and local attackers to install malware or compromise a system.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-1703-is-now-end-of-service-no-more-security-updates/