Firefox 60 (the current release) displays an “untrusted connection” error for any website using a TLS/SSL certificate issued before June 1, 2016 that chains up to a Symantec root certificate. This is part of the consensus proposal for removing trust in Symantec TLS certificates that Mozilla adopted in 2017. This proposal was also adopted by the Google Chrome team, and more recently Apple announced their plan to distrust Symantec TLS certificates. As previously stated, DigiCert’s acquisition of Symantec’s Certification Authority has not changed these plans.

In early March when we last blogged on this topic, roughly 1% of websites were broken in Firefox 60 due to the change described above. Just before the release of Firefox 60 on May 9, 2018, less than 0.15% of websites were impacted – a major improvement in just a few months’ time.

The next phase of the consensus plan is to distrust any TLS certificate that chains up to a Symantec root, regardless of when it was issued (note that there is a small exception for TLS certificates issued by a few intermediate certificates that are managed by certain companies, and this phase does not affect S/MIME certificates). This change is scheduled for Firefox 63, with the following planned release dates:

Beta – September 5

Release – October 23

We have begun to assess the impact of the upcoming change to Firefox 63. We found that 3.5% of the top 1 million websites are still using Symantec certificates that will be distrusted in September and October (sooner in Firefox Nightly)! This number represents a very significant impact to Firefox users, but it has declined by over 20% in the past two months, and as the Firefox 63 release approaches, we expect the same rapid pace of improvement that we observed with the Firefox 60 release.

We strongly encourage website operators to replace any remaining Symantec TLS certificates immediately to avoid impacting their users as these certificates become distrusted in Firefox Nightly and Beta over the next few months. This upcoming change can already be tested in Firefox Nightly by setting the security.pki.distrust_ca_policy preference to “2” via the Configuration Editor.