Ref: NoScript and other popular Firefox add-ons open millions to new attack NoScript, Firebug, and other popular Firefox add-on extensions are opening millions of end users to a new type of attack that can surreptitiously execute malicious code and steal sensitive data, a team of researchers reported. The attack is made possible by a lack of isolation in Firefox among various add-ons installed by an end user. The underlying weakness has been described as an extension reuse vulnerability because it allows an attacker-developed add-on to conceal its malicious behavior by invoking the capabilities of other add-ons. Instead of directly causing a computer to visit a booby-trapped website or download malicious files, the add-on exploits vulnerabilities in popular third-party add-ons that allow the same nefarious actions to be carried out. Nine of the top 10 most popular Firefox add-ons contain exploitable vulnerabilities. By piggybacking off the capabilities of trusted third-party add-ons, the malicious add-on faces much better odds of not being detected. Of the top 10 most popular add-ons vetted by Mozilla officials and made available on the Mozilla website, only Adblock Plus was found to contain no flaws that could be exploited by a malicious add-on that relied on reuse vulnerabilities. Besides NoScript, Video DownloadHelper, Firebug, Greasemonkey, and FlashGot Mass Down all contained bugs that made it possible for the malicious add-on to execute malicious code. Many of those apps, and many others analyzed in the study, also made it possible to steal browser cookies, control or access a computer's file system, or to open webpages to sites of an attacker's choosing.