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Tor browser fixes bug that allows JavaScript to run when disabled – Naked Security

Source: National Cyber Security – Produced By Gregory Evans

The Tor browser has fixed a bug that could have allowed JavaScript to execute on websites even when users think they’ve disabled it for maximum anonymity.

The Tor Project revealed the issue in the release notes for version 9.0.6, initially suggesting users manually disable JavaScript for the time being if the issue bothered them.

That was subsequently revised after the NoScript extension – used by Tor to control the execution of JavaScript, Java, Flash and other plugins – was updated to version 11.0.17.

Whether the issue matters depends on how users have configured Tor to treat JavaScript.

Tor’s ‘standard’ setting enabled JavaScript by default, which users can upgrade to either ‘safer’, which disables JavaScript on non-HTTPS sites, or ‘safest’, which disables JavaScript completely.

Each setting has its pros and cons. Leaving JavaScript enabled opens users to the hypothetical risk that their anonymity might be compromised, for example using a vulnerability in the underlying Firefox browser.

There have been a small number of reports of this happening, for example in 2013, and again in 2016 when Mozilla issued a patch to fix a real-world JavaScript attack aimed at Tor by a government. On the other hand, many websites rely on JavaScript and disabling it can cause them to break, or at least work less well.