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
(thanks Krzysztof Kotowicz and Sebastian Lekies for their
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