The caching of static files is controlled in the web.config file, in the staticContent section. By default, the maximum caching period is 31 days. This affects both browsers and CDNs. To invalidate the cache for static resources, you need a cache-busting strategy for the required types. Sitefinity has a built-in cache busting mechanism for JavaScript files that are stored in resource package folders. However, it does not cover CSS files or files outside of these folders.