NoScript

NoScript

NoScript extension icon and main menu
Developer(s)	Giorgio Maone
Stable release	2.9.5.2 (November 28, 2016 (2016-11-28)[1]) [±]
Preview release	2.9.5.2rc5 (November 28, 2016 (2016-11-28)[2]) [±] Firefox for Android 3.5a14 (August 3, 2016 (2016-08-03)[3]) [±]
Repository	no%20value
Written in	JavaScript, XUL, CSS
Available in	45[4] languages
Type	Mozilla extension
License	GPLv2+
Website	NoScript.net

NoScript (or NoScript Security Suite) is a free and open-source extension for Mozilla Firefox, SeaMonkey, and other Mozilla-based web browsers, created and actively maintained by Giorgio Maone,^[5] an Italian software developer and member of the Mozilla Security Group.^[6] NoScript allows executable web content such as JavaScript, Java, Flash, Silverlight, and other plugins only if the site hosting is considered trusted by its user and has been previously added to a whitelist. NoScript also offers specific countermeasures against security exploits.^[7]

Features

Security and usage

NoScript blocks JavaScript, Java, Flash, Silverlight, and other "active" content by default in Firefox. This is based on the assumption that malicious websites can use these technologies in harmful ways. Users can allow active content to execute on trusted websites, by giving explicit permission, on a temporary or a more permanent basis. If "Temporarily allow" is selected, then scripts are enabled for that site until the browser session is closed.

Because many web browser attacks require scripting, configuring the browser to have scripting disabled by default reduces the chances of exploitation. Blocking plug-in content, as well, helps to mitigate any vulnerabilities in plug-in technologies, such as Java, Flash, Acrobat, and so on. NoScript will replace these blocked elements with a placeholder icon. Clicking on this icon enables the element.^[8]

NoScript takes the form of a toolbar icon or status bar icon in Firefox. It displays on every website to denote whether NoScript has either blocked, allowed, or partially allowed scripts to run on the web page being viewed. Clicking or hovering (since version 2.0.3rc1^[9]) the mouse cursor on the NoScript icon gives the user the option to allow or forbid the script's processing.

NoScript also may provide additional defenses against web-based attacks such as XSS, CSRF, clickjacking, man-in-the-middle attacks, and DNS rebinding, with specific countermeasures that work independently from script blocking.^[10]

Site matching and whitelisting

NoScript Anywhere 3.5a8 site permissions in Firefox for mobile 38 on Android 2.3

Scripts (and other blockable elements) are allowed or blocked based on the source from where the script is fetched. Very often, this source is not identical to the URL displayed in the address field of the web page (main page). This is because many web pages fetch elements such as iframes, style sheets, scripts, and embeddable objects from remote sites. When a web page includes scripts and other blockable elements from many sources, the user may specify blocking policy for the main address and each of the sources separately.

No scripts are executed, if the address of the main page is untrusted. Once any source is marked as trusted, NoScript will regard it as trusted even if it is loaded indirectly by web pages or scripts originating from other domains.

The possibility to allow scripts coming from a certain source only for specific main page locations has been requested frequently, but is not yet easy to configure. It may be achieved by configuring the built-in ABE module to fine-tune cross-site resource access.^[11]

For each source, the exact address, exact domain, or parent domain may be specified. By enabling a domain (e.g. mozilla.org), all its subdomains are implicitly enabled (e.g. www.mozilla.org, addons.mozilla.org and so on) with every possible protocol (e.g. HTTP and https). By enabling an address (protocol://host, e.g. https://mozilla.org), its subdirectories are enabled (e.g. https://mozilla.org/firefox and https://mozilla.org/thunderbird), but not its domain ancestors nor its siblings. Therefore, mozilla.org and addons.mozilla.org will not be automatically enabled.^[12]

Untrusted blacklist

Sites can also be blacklisted with NoScript.^[13] This, coupled with the "Allow Scripts Globally" option, lets users who deem NoScript's "Default Deny" policy too restrictive, to turn it into a "Default Allow" policy.^[14] Even if the security level is lower than in the default configuration, NoScript still provides a number of defenses against certain web-based attacks, such as cross-site scripting, CSRF, clickjacking, man-in-the-middle attacks, and DNS rebinding.^[10]

Anti-XSS protection

On April 11, 2007, NoScript 1.1.4.7 was publicly released,^[15] introducing the first client-side protection against Type 0 and Type 1 Cross-site scripting (XSS) ever delivered in a web browser. Whenever a website tries to inject HTML or JavaScript code inside a different site, NoScript filters the malicious request, neutralizing its dangerous load.^[16] Similar features have been adopted years later by Microsoft Internet Explorer 8^[17] and by Google Chrome.^[18]

Application Boundaries Enforcer (ABE)

The Application Boundaries Enforcer (ABE) is an inbuilt NoScript module meant to harden the web application oriented protections already provided by NoScript, by delivering a firewall-like component running inside the browser. Important --- site must be in the whitelist! If it isn't, ABE will ignore your rule about that site. This "firewall" is specialized in defining and guarding the boundaries of each sensitive web application relevant to the user (e.g. plugin, webmail, online banking and so on), according to policies defined either directly by the user, or by the web developer/administrator, or by a trusted third party.^[19] In its default configuration, NoScript's ABE provides protection against CSRF and DNS rebinding attacks aimed at intranet resources, such as routers or sensitive web applications.^[20]

ABE can protect browser plugins from being exploited, something that cannot be done by uBlock. However, in most cases plugins are unnecessary in web browsers, and security experts recommend that it not be run in a browser unless absolutely necessary. It was suggested that, if plugins are required by a few Web sites, users should have a separate browser installation specifically for those sites.

ClearClick (anti-clickjacking)

NoScript's ClearClick feature,^[21] released on October 8, 2008, prevents users from clicking on invisible or "redressed" page elements of embedded documents or applets, defeating all types of clickjacking (i.e. frame-based and plugin-based).^[22] This makes NoScript "the only freely available product which offers a reasonable degree of protection" against clickjacking attacks.^[23]

HTTPS enhancements

NoScript can force the browser to always use HTTPS when establishing connections to some sensitive sites, in order to prevent man-in-the-middle attacks. This behavior can be either triggered by the websites themselves, by sending the Strict Transport Security header, or configured by users for those websites which don't support Strict Transport Security yet.^[24] NoScript's HTTPS enhancement features have been used by the Electronic Frontier Foundation as the basis of its HTTPS Everywhere add-on.^[25]

Surrogate scripts

NoScript is able to run user-provided scripts instead of, or in addition to, website-provided scripts, in a similar manner to the Greasemonkey addon. This feature was originally designed to fix pages that make use of third-party scripts (such as Google Analytics) in a way that causes the pages to break when the third-party scripts are blocked, but is not required for the actual functionality of the page.^[26] The list of built-in surrogate scripts is actively maintained^[27] and included 48 sites as of version 2.6.9.27.

Unintended benefits

NoScript provides some unintended benefits. Since ads tend to be rich graphics and multimedia served via JavaScript and plugins, use of NoScript (which blocks the JavaScript) can reduce bandwidth consumption by approximately 42%.^[28] In addition, the use of NoScript reduces the amount of system resources required by the browser to display web pages.

As some web tracking services depend on JavaScript, and as JavaScript exposes browser and operating system configuration details, NoScript can increase privacy and anonymity as seen via the EFF's Panopticlick tool.^[29] NoScript also can be used by web developers as a convenient way to test how well sites work without JavaScript, particularly since modern versions of Firefox have removed JavaScript controls from the regular configuration pane.^[30]

Awards

• PC World chose NoScript as one of the 100 Best Products of 2006.^[31]
• In 2008, NoScript won About.com's "Best Security Add-On" editorial award.^[32]
• In 2010, NoScript was "The Reader's Choice Awards" winner in the "Best Privacy/Security Add-On" category at About.com.^[33]
• In 2011, for the second year in a row, NoScript was "The Reader's Choice Awards" winner in the "Best Privacy/Security Add-On" category at About.com.^[34]
• NoScript was the 2011 (first edition) winner of the Dragon Research Group's "Security Innovation Grant". This award is given to the most innovative project in the area of information security, as judged by an independent committee.^[35]

Controversies

Conflict with Adblock Plus

In May 2009, it was reported that an "extension war" had broken out between NoScript's developer, Giorgio Maone, and the developers of the Firefox ad-blocking extension Adblock Plus after Maone released a version of NoScript that circumvented a block enabled by an AdBlock Plus filter.^[36][37] The code implementing this workaround was "camouflaged"^[36] to avoid detection. Maone stated that he had implemented it in response to a filter that blocked his own website. After mounting criticism, and a declaration by the administrators of the Mozilla Add-ons site that the site would change its guidelines regarding add-on modifications,^[38] Maone removed the code and issued a full apology.^[36][39]

Conflict with Ghostery

Also in May 2009, shortly after the Adblock Plus incident,^[40] a spat arose between Maone and the developers of the Ghostery add-on after Maone implemented a change on his website that disabled the notification Ghostery used to report web tracking software.^[41] This was interpreted as an attempt to "prevent Ghostery from reporting on trackers and ad networks on NoScript's websites".^[40] In response, Maone stated that the change was made because Ghostery's notification obscured the donation button on the NoScript site.^[42]

The conflict was resolved when Maone changed his site's CSS to move—rather than disable—the Ghostery notification.^[43]

See also

• Firefox privacy extensions
• NotScripts
• GNU LibreJS
• HTTP Switchboard
• Content Security Policy
• Framekiller
• Flashblock

References

External links

• Official website
• NoScript at addons.mozilla.org
• NoScript Anywhere (3.5a8) for Firefox for Android
• NoScript presentation in How to Bypass Internet Censorship, a FLOSS Manual, 10 March 2011, 240 pp.