We need to use java scripts on some sites because we need them in order to get the task done. Suppose some site get my real IP address by using some java script attack, then how dangerous it can be? My IP address is a static not a variable one. It is different everytime and shows location several miles away each time than the last time. Maximum it shows a city and the name of my ISP. If my adversary is someone like the NSA or FBI can they use this info to get me? Edit: I am using Tails and it protects against the fingerprinting. So even they install something on my system for attacking me in the long term, it will get deleted everytime I reboot or shut down my system, right?
The NSA or the FBI (or the equivalent agency in your country), if they suspect illegal activity, can contact your ISP with a subpoena. Your ISP is legally bound to give requesting agencies the name and address of the person paying the bill. It is an extreme case, but it can be done.
You need to take some additional measures to keep a global adversary at bay.
Connect to internet at a public place which does not employ a security camera.
Use internet at that place only for one day and never use that place for internet connection again. This public places you use for internet connection need to be at least 100 miles away from your place of residence, and work or study.
Use Tails on a brand new notebook that you use for nothing else except for this purpose and get ride of the notebook's hard drive.
You need to isolate each activity from any other activity all the times. The best practice is to reboot the Tails after each separate activity.
Do not use internet for more than few hours at each location.
Use encryption all the time.
Pay attention to your surrounding at all times. If it does not feel right, move from that place.
leave your cellphone or any comminiucation device you carry at home.
Finally have a back up plan in case you are caught.
And yes, The IP address is more than enough information to catch you if you are wanted.