Yoast SEO was updated to version 2.3.1, from version 2.3. Changelog:
- Makes sure authors and editors cannot submit advanced metadata on a post when the advanced tab in the metabox has been disabled for them.
- Fixes a bug where upgrading to version 2.3 would occasionally cause WSOD’s on both admin and frontend. We were unable to pinpoint the exact conflicting plugins and themes, but we are quite confident it was caused by us using, and others hooking into, WP_Query too early.