Official Google Webmaster Central Blog

Site operators are strongly encouraged to make the necessary changes to their sites before the First Canary release for Chrome 66 and 70 and no later than the corresponding Beta release dates. The first impact from a given release will coincide with the First Canary reaching a steadily widening audience as the release hits Beta and then ultimately Stable. If connecting to your site displays a certificate error or a warning in DevTools as shown below you'll need to replace your certificate. Accessing a site serving such a certificate will fail and the request will be blocked as of Chrome 65. We previously announced plans to deprecate Chrome's trust in the Symantec certificate authority including Symantec-owned brands like Thawte VeriSign Equifax GeoTrust and RapidSSL.  Read more