SAML Message Decoder од Magnus Suther

This tool helps you debug your SAML based SSO/SLO implementations. It runs in the background, collecting SAML messages as they are sent and received by the browser. When something didn't work as expected, just pop up the extension to view the latest SAML messages in cleartext (easily readable XML). This allows you see what happened, and to get an idea of how to solve those weird authorization issues.