A fix has been implemented. The mitigation is automatic on Xenial, but Trusty sites will have to update to Xenial or Focal in order to mitigate. We'll continue to monitor for a while before resolving the incident.
Posted Sep 30, 2021 - 18:25 UTC
We identified the root cause to be an outdated root certificate. We’re in the process of releasing an updated build image.
Posted Sep 30, 2021 - 17:44 UTC
We are continuing to work on a fix for this issue.
Builds using the Xenial and Trusty versions of our build image (configured in each site's Deploy Settings page) that require a download of yarn are failing. This will impact only builds without an already-cached copy of yarn. We're working on a fix but in the meantime, builds on our newer (default) Focal build image are not affected; you can update to the new image to work around this immediately.