BApp details: WebSphere Portlet State Decoder
This extension displays the decoded XML state of a WebSphere Portlet in a new tab when the request is viewed.
Upon clicking the tab, the extension makes a request against an endpoint on the application server which decodes the URL, formats the resulting XML, and displays it in the tab.
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.