09:50 UTC, December 13 - This issue has been resolved. It affected web stores using new commercebuild staging domains. We have added checks on these domains to ensure SSL certificates remain valid.
19:30 UTC - We are aware of an issue affecting images on some web stores, as well as the accessibility of some staging web stores. This issue is occurring due to expired/invalid SSL certificates. We have escalated this issue to our systems team and are awaiting resolution. The internal ticket for this issue is XMECOM-9755. Thank you for your patience!