BApp details: Site Map Fetcher
This extension fetches the responses of unrequested items in the site map.
When browsing a target, Burp adds to the site map any items that are inferred from actual responses. Some of these items may never get requested, and will show up as gray in the site map. This extension takes care of those by requesting each of them and adding its response to the site map. No more gray nodes in Burp's site map!
You can install BApps directly within Burp, via the BApp Store feature in the Burp Extender tool. You can also download them from here, for offline installation into Burp.
Please note that extensions are written by third party users of Burp, and PortSwigger Web Security makes no warranty about their quality or usefulness for any particular purpose.