No, the person using the browser that loads the scripts is the user. The user has the option to disable JavaScript, so they are responsible for whatever they allow to be run on the machine.
If you don't trust yourself to use the web safely, then put limits on what a naughty script can do. One option is to disable hyperthreading.
If you don't trust yourself to use the web safely, then put limits on what a naughty script can do. One option is to disable hyperthreading.