Atlassian have verified that there was a bad Jira Cloud deploy this morning. They are now rolling back this deployment.
We'll continue to monitor error rates until this has been completed.
Posted Dec 07, 2018 - 13:37 AEDT
Investigating
Since about 9:15 AM AEST, we're observing elevated error rates, authenticating webhooks requests from Jira Cloud. This seems to be caused by a breaking API change on Jira Cloud's side.