Mozilla has adopted a proposal to remove trust in all Symantec certificates from Firefox. The proposal includes a number of phases designed to minimize the impact of the change to Firefox users. The change is already in effect in Firefox Nightly and Firefox 60 is expected to be released on May 9th, 2018. In the final version of Firefox 60, trust will be removed for all Symantsec certificates issued prior to June 1st, 2016, with the exception of certificates issued by a few subordinate CAs controlled by Apple and Google.”]
Source: https://blog.mozilla.org/security/2018/03/12/distrust-symantec-tls-certificates/