(Original Title: cache-control: must-revalidate not always given on RTE Javascript response)

Explanation by Tom Davies: The Rich Text Editor Javascript is retrieved as a two-step process, and the generated Javascript is cached on the server.

The first set of Javascript to be returned needs to have a must-revalidate header to pick up changes in the base url Confluence is deployed at. The header was only being applied to responses where the cache was empty, not to all responses, so the rich text editor would fail to load for users who had incorrect javascript cached in their browser.