Google has announced that it will withdraw its trust from Symantec CAs (certification authorities) from 2018. A corresponding article can be found in the Google Security Blog:
Specifically, this means that websites or services that work with certificates issued by Symantec are no longer considered trustworthy by Chrome, which affects all certificates issued by Symantec before June 1, 2016. This also affects the certificates of the other certification authorities operated by Symantec: Thwate, Verisign, Equifax, GeoTrust and RapidSSL. Symantec was previously the market leader and the certification authority and is now selling the certificate business to DigiCert.
A relatively expensive wildcard certificate from Thwate, which was issued in May 2016 and would actually still be valid until May 2019, loses a good half of its term. Great thing...
The exact dates when Chrome will no longer trust the Symantec certification authorities can be found in the article linked above. Other browsers will probably continue to trust Symantec for the time being. However, Chrome will respond with the nice warning for the foreseeable future:
Free SSL certificates, which are also supported by all common operating systems and browsers, are available from Let's Encrypt. From January 2018, Let's Encrypt also plans to issue wildcard SSL certificates.