We're on version 7.x and the upgrade assistant gives the following output:

You have 1 index patterns (cf-http-*...) that use scripted fields. Scripted fields are deprecated and will be removed in future. Use runtime fields instead.

Issues reported by the upgrade assistant must fixed before upgrading to v8. Seems like multiple fields are scripted. That logic will likely need to be moved from scripted fields to either runtime fields or the ingest pipeline.

Reference:
https://www.elastic.co/de/blog/introducing-elasticsearch-runtime-fields
https://www.elastic.co/guide/en/elasticsearch/reference/7.17/runtime.html