How to get JSESSIONID value from Chrome browser?
One answer
The JSESSIONID is a Cookie that you can find in the Request details.
You should use other tools if you try to experiment with REST calls. See https://rsjazz.wordpress.com/2019/05/13/using-a-rest-client-to-authenticate-to-elm-clm-applications/ .
The Cookie JSESSIONID returned is required to be passed in a header JSESSIONID in some cases. If not provided the tool assumes a cross site scripting attack, if I remember correctly. Not sure when this is needed, but I think the error message hints it.