As I mentioned in my original article on Firefox extensions, the web browser has become a critical component of the computing experience for many users. Modern browsers have evolved into powerful and extensible platforms, and extensions can add or modify their functionality. Extensions for Firefox are built using the WebExtensions API, a cross-browser development system.
In the first article, I asked readers: "Which extensions should you install?" To reiterate, that decision largely comes down to how you use your browser, your views on privacy, how much you trust extension developers, and other personal preferences. Since that article was published, one extension I recommended (Xmarks) has been discontinued. Additionally, that article received a ton of feedback that has been taken into account for this update.
Once again, I'd like to point out that browser extensions often require the ability to read and/or change everything on the web pages you visit. You should consider the ramifications of this very carefully. If an extension has modify access to all the web pages you visit, it could act as a keylogger, intercept credit card information, track you online, insert advertisements, and perform a variety of other nefarious activities. That doesn't mean every extension will surreptitiously do these things, but you should carefully consider the installation source, the permissions involved, your risk profile, and other factors before you install any extension. Keep in mind you can use profiles to manage how an extension impacts your attack surface—for example, using a dedicated profile with no extensions to perform tasks such as online banking.