Like most software these days there are support forums and firefox is no different. Whilst doing one of my irregular wanders through the firefox support forum I came across this thread which talks about the dangerous extensions one should be aware of as containing spyware or at the very least track users without having pre-advised them of this.

As with most things you get a choice and here it’s to install or not. The list of 93 known bad extensions is something I plan to keep an eye on – for my part I only use 10 or so extensions with only 3 or 4 of those on a daily basis and thankfully none of mine are in the list!

The main point here is to be careful what you install.