An access check is performed on the cached value to ensure that a user has permission to see the included content before it is rendered, but this permission check is based only on Confluence permissions for the source of the original content (page permissions for the page with the MultiExcerpt on it).
Therefore, all users who have permission to see the excerpt content (based on Confluence permissions) will have access to the cached value.This works for most scenarios but imagine a complex scenario in which you are nesting 3rd party macros in your MultiExcerpt that either restrict their content using something other than the Confluence restrictions for the page they are on or the 3rd party macros do something like render content that differs per-user. In such a scenario you would want to disable the cache for your MultiExcerpt Include macro.
Another scenario where you may want to disable the cache for a MultiExcerpt Include is when you are including complex content that is subject to intermittent responses from whatever service(s) are behind them and/or the included content is implemented with poor/unreliable error handling and is prone to occasionally render “bad” responses. Such “bad” responses are normally solved in web apps with a page refresh and may not be noticed often enough by your users for them to report it to you. However, if a bad response ends up in the MultiExcerpt Include cache then it will become more noticeable.
The admin tool allows you to flush the cache anytime, but if you ever encounter intermittent problems with rendering any included content that comes from 3rd party macros then consider disabling the MultiExcerpt cache. You can either disable the caching per MultiExcerpt Include or globally. We recommend you disable it at the MultiExcerpt level so that you have the flexibility you need depending on your usage and your environment.