Researchers say that attackers could use holes in Firefox add-ons to target your PC

Researchers from Northwestern University discover how an attacker could write a malicious Firefox add-on that takes advantage of security holes in other Firefox add-ons to do its bidding. It goes without saying that any given piece of computer code, be it an app, a part of your operating system, or even a browser plug-in—may contain flaws that could leave your PC open to attack. But a team of researchers from Northwestern University have come across a new method of attack that can take advantage of holes in one or more installed Firefox add-ons.

According to the team’s research paper (PDF), this newly discovered attack “leverages capability leaks from legitimate extensions to avoid the inclusion of security-sensitive API calls within the malicious extension itself.”

Put another way: Firefox doesn’t enforce any isolation between the add-ons you install, as Ars Technica notes, which could potentially result in security problems. As a result of this lack of isolation, researchers say, an attacker could write a malicious Firefox add-on that appears harmless, but can use security flaws in other installed add-ons to do its bidding. In this sort of attack, the malicious add-on itself might not raise and security red flags, but it may still be able to wreak havoc on your PC. The implications of these so-called “extension-reuse vulnerabilities” are potentially serious, especially if you consider that, according to the research paper, “nine of the top 10 extensions contain a large number of such vulnerabilities” and that fact that it may only take “only one or two vulnerabilities” to launch an attack against your PC.

That said, the paper doesn’t get into the exact risk of an attack on any particular system, and measuring risk might be tricky given how different users will have a different combination of add-ons installed. That is, it’s relatively easy to attack a vulnerability in one popular piece of software, such as Flash Player. It’s more difficult to attack a combination of vulnerabilities at once because it’s less likely that all potential targets will have all the necessary add-ons installed. Still, this is one area of security research we’ll want to watch closely.