NoScript is an add-on for Firefox that blocks JavaScript, Java, Flash, and other plugin content (allowing you to selectively re-enable them for certain sites). It also offers cross-site scripting protection. This is mainly designed to keep web users safe, but security testers can also use the add-on to see what scripts a site is using. One caution is that the NoScript author Giorgio Maone has been caught inserting hidden code into NoScript which disabled users' ad-blocking software so that ads would still show up on the NoScript web site. He did post a lengthy apology.
