If you haven't updated in a while, check out the Terminus Changelog to see what's new and update to the current release.
Pantheon release notes
Terminus 1.4.0
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Pantheon Upstream Configuration
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Organizations utilizing a Custom Upstream can now set default site configurations, such as nested docroot, in the pantheon.upstream.yml file. For details, see Pantheon YAML Configuration Files.
New Relic
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New Relic's APM Availability Monitoring has known incompatibilities with SNI, which our HTTPS uses. Instead, we recommend configuring the free availability monitoring service within New Relic’s Synthetics Lite tool. For details, refer to New Relic APM Pro.
Documentation
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Default PHP Versions
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Core Upgrades
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Drupal 8.3.4, Drupal 7.56, and WordPress 4.8 have been pushed to all Site Dashboards.
Drupal 8.3.3 and above hooks into the Pantheon service provider, to support operations such as clearing Pantheon’s edge cache when Drupal cache is rebuilt.
Platform Security
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CVE-2016-8332
Pantheon has deployed new versions of Ghostscript and Openjpeg2 to mitigate the CVE-2016-8332 vulnerability. No user action is required.
CVE-2017-8295
The platform is not vulnerable to this exploit, no user action is required.
PHP Upgrade
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We upgraded PHP to 7.0.18. See our documentation to learn how to upgrade your PHP version.