Question about ScriptBlock

[SimplySimple]

Hello All,

I have a question that was raised when I was looking into the anonymity of tor.
Basically I read,
That using ScriptBlock, no-script, etc. can be identifying.
Because when you whitelist sites, that whitelist travels with you to new sites.
So someone would be able to see the same whitelist going site to site.


What I don't understand is how the fuck does the site I'm going to know what sites I have whitelisted? Isn't that list kept locally and never given out?

Thank you,
Simple

EDIT: Just went though my whole history and can't find the site where I read this, ugh, how helpful.
EDIT2: Found it through Google
https://www.torproject.org/docs/faq.html.en#TBBJavaScriptEnabled

[HardCodedShadow]

On a website you may have many different scripts running. If you whitelist only scripts coming from certain websites, it may act as a sort of figerprint if you see what I mean.
The server can check if the script was executed or not to see your whitelisted websites/services.
This means if you visit few sites and allow script executing on them, other websites can try to detect your whitelisted websites and thus distinguish you as an individual.