Browsers and root program owners have plans to remove trust of all legacy Symantec SSL/TLS certificates issued under the Symantec infrastructure. Websites and applications secured with these legacy Symantec SSL/TLS certificates trigger security warnings in browsers and applications relying on its root store:
More details from Google, Mozilla, Apple, Microsoft, and Oracle:
Google security blog
Mozilla security blog
Apple information about distrusting Symantec certificate authorities
Microsoft partners with DigiCert to begin deprecating Symantec TLS certificates
Oracle's Plan for Distrusting Symantec TLS Certificates in the JDK
DigiCert blog regarding Apple distrust
Symantec TLS/SSL certificates affected by distrust are based on their issuance date. Refer to this table and check your certificate inventory for certificates at risk of potential distrust.
Note:
Apple
Oracle Java
Enterprise customers
Also distrusted - Certificates issued from the legacy Symantec root hierarchy on or after December 1, 2017
For uninterrupted business continuity, some Managed PKI for SSL customers continue to issue certificates from the legacy Symantec root hierarchy after the December 1, 2017 switch to the DigiCert hierarchy. These certificates are already distrusted by Google Chrome and will be distrusted by Apple on August 1, 2018.