We upgraded elasticsearch/kibana to 7.8 from 7.7. All went well, except for one weird thing. If I go into discover and look at documents (all server logs) in one of our indices (using the table view), kibana is not only showing the fields actually in the index, but also a few dozen other fields, all date fields for some reason. Things like cef.extensions.agentReceiptTime, misp.threat_indicator.valid_from, etc etc. Dozens of them. If I fetch that same document through the API, those fields of course don't exist. It's just kibana showing them.
Any idea what this could be and how to get rid of it?