Web plugins such as Flash, Java and JavaScript can be used to add a range of interesting features to web sites, but there are also a number of downsides. In addition to reducing the performance of sites, there is also the potential for scripts to be used for malicious purposes. NoScript is a Firefox addon that can be used to prevent the running of scripts on the sites you visit.

The addon automatically blocks all such content, but there may well be occasions when you need it to run. When you encounter such as site, you can easily add it to a whitelist so that scripts will be allowed to run now and in the future - ideal for banking and shopping sites.

You can choose to be notified when a script is blocked, so should a site fail to function as expected you can opt to enable individual page elements as required. The settings you choose to use can be quickly backed up by saving them as a bookmark so they can be restored when you have to reinstall, or transferred to another computer.

With hardly any user intervention required, NoScript offers a superb level of protection against site borne security threats and ensures that you have full control over what is allowed to run in your browser window.

Version 5.0 (changelog):

+ [XSS] Added countermeasures against several vectors
  exploiting client-side JavaScript templating frameworks
  (thanks Krzysztof Kotowicz and Sebastian Lekies for their
  research)
x [XSS] Fixed e10s-related regression in window.name
  sanitization (thanks Krzysztof Kotowicz for reporting)
x Fixed "Allow local links" breaking file:/// URL loading in
  Gecko 53 and above
x Fixed JSON viewer working only on JavaScript-enabled URLs

Verdict

A small and simple addon that places you firmly in control of the web sites you visit