Security Review : Add-ons

By kosh at 9:14 pm on February 13, 2009 | 1 Comment

An add-on is a simple plugin that you use, say for firefox, to let you do your work more easily. This also lets you customize the browser in ways that do not affect the productivity of other people. Add-ons are becoming a major part of the browser functionality but sans the scrutiny that goes into developing a browser.

Assets and Security Goal:

* Assets: Your browser, everything that you use it for and your cookies. Uh, not the ones you eat. and privacy.
* Security Goal: Protect your privacy at all cost and your cookies and your intimate browsing secrets!

Adversaries and Threats:

* Unauthorized publishers: This is the dreaded group of publishers that are able to make an add-on for your browser and pass it off as being legitimate and harmless. This is much easier than you think since most add-ons are unverified or rather community verified and it might take a while to find an exploit.


* Counterfeit add-ons are the biggest risk – a majority of the add-ons are through unverified authors.
* Deceived by community rating. Since the rating for the plugins is done by the community, an obscure/malicious add-on can be easily made to look like a legitimate one through a community of attackers/ an attacker with a community of profiles.
* Unauthorized plugins from third party websites.


* Other legitimate users – These are probably the best and most formidable defense when it comes to validating add-ons. However, this also a delayed defense since ‘enough’ users will have had to use the add-on for someone to finally detect a malicious exploit.
* Firewall – Your firewall is also your second line of defense when preventing backdoor access through the malicious add-on
* Antivirus software – An up-to-date virus definition file should help the software detect a malicious plugin. However, this also assumes that the attacker used a known exploit/trojan/virus to inject into the add-on.
* Security updates from the browser, OS – These can help patch the exploits that are currently in place.

The risk of being duped means to lose a significant amount of personal information that is stored in the browser. With the shift of browser towards acting like an OS with features to save passwords,sessions, etc, there is an unbelievable amount of personal information that can be stolen through a malicious add-on. The add-on can also redirect to malicious websites that involve elaborate phishing scams leading to the loss of information and money. Such attacks give the hacker a complete control of your online portfolio which can be held for ransom and also misused, causing personal damage.

Overall, although there are inherent risks to open source projects like a community browser, a large part of the attacks are easily mitigated due to the sheer number of users that pass through such an add-on. There also seems to be significant,active and unofficial community that monitors the plugins for malicious intent. One way to decrease the probability of such an attack would involve letting a significant time pass from the release of the plugin to the installation for it to be tested by active community members. Filtering the installation of add-ons also becomes an important but often impossible task in a corporate environment where the risks are especially high. Add-ons(unsigned) are definitely a double edged sword that need to be dealt with care.

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1 Comment

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    Comment by Joshua Barr

    February 20, 2009 @ 4:45 pm

    Good security review.

    Compromise by this route can definitely happen. I believe that my own Firefox installation has become compromised at some point. Whatever it is seems to be designed to attack Windows machines, as I occasionally find strangely named .zip and .exe files in my Firefox Downloads directory, but since I don’t make a practice of executing strange binaries (and don’t run the right operating system) I’ve been safe so far.

    I haven’t been able to discover yet what exactly became compromised, or how, but this was a definite awakening to me that risk is there. I have a fairly small, conservative list of well-vetted add-ons and use secure browsing tactics and still (apparently) was vulnerable to something.

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