
Disabling JavaScript causes many web sites to be unusable, thus it is enabled by default.Īs a best practice, one should disable JavaScript in the Tor browser and keep NoScript enabled for all sites, unless you have an extremely compelling reason not to. Many Tor users are not technically savvy, and JavaScript is commonly used with HTML5 in modern web sites. The only reason the Tor project allows JavaScript to be on by default in the Tor browser is usability. JavaScript), then they may be hard pressed to find a viable exploit even if they have access to zero days etc. In the schema browser, you normally create a query in a specific folder i.e. If the vectors for these zero-days are disabled (e.g. the FBI), they have access to zero-day exploits. In the case of a serious adversary like a state-backed entity (e.g. In general, enabling JavaScript opens the surface area for many more potential attacks against a web browser. Disabling JavaScript causes many web sites to be unusable, thus it is enabled by default. You can read more about it in Ars Technica. The only reason the Tor project allows JavaScript to be on by default in the Tor browser is usability. Now click on Cookies and site permissions in the left-hand Settings pane. Choose the Settings item on the Menu tab. This caused the computers to call back to an FBI server from their real, non-anonymized IP, leading to the deanonymization of various users. Click on the three-dot icon in the top right corner to open the Menu tab. The FBI kept servers online, and then installed javascript paylods which exploited a zero-day exploit in Firefox.

The first major incident where this happened was with the "Freedom Hosting" seizure by the FBI.

There are a number of known vulnerabilities, that have been used, to deanonymize Tor users via leveraging JavaScript.
