SOLUTIONS for the uninformed:
Anti-virus will normally detect malicious scripting when inspecting browser add-ons and BHOs, so you are probably safer from these vectors than the OP suggests.
But additionally:
There is somewhat of a rift between what is called 'virus' and what is called 'adware' which oddly enough goes all the way back to the rift between virus software and trojan hunting software... Back in the day, trojan hunters were better at ripping adware than their virus software counterparts. These privacy stealers, or spyware are descendant from the adware, which are in turn descendant from trojans, roughly speaking.
So, like in kind, adware protection software, such as Malwarebytes, Spybot Search and Destroy, SuperAntiSpyware, and others, often have an edge over antivirus based software in the methods they use, and offer a more aggressive means against adware, which includes a very aggressive routine against Browser vectors.
I have always maintained that a good antivirus should be backed up with a good anti-spyware (anti-adware) software. Now, that anti-spyware does not need to be running all the time, and on my boxen, they don't. I use
Malwarebytes primarily, and it is set up to only run manually, with none of the bells and whistles otherwise engaged.
In part that is because any antivirus will do a fair job anyway, and you are only looking for a pinch-hitter... And in part, it is to keep my manual hands involved in this very important aspect of computing... And lastly in part, because the performance hit from running yet another background scanner would piss me off.
So I just make it a point to schedule a time for a nice cup of tea, supervising manual scans on all my hardware every couple weeks, and leave the realtime scanners off (other than antivirus which runs all the time).
In addition, I maintain an anti-virus/trojan cleanup engine, in the same manner. A cleanup engine is a hardened manual scanner that is used my people like me to clean up already-infected machines.
EmsiSoft's EEK Emergency kit lives in the root of my drive, and during that manual scan session, I always wake it up too, letting it update itself, and occasionally, like maybe every third or fourth time, I will let it scan too. Just like with doctors, a second opinion is always good, and just like with coats, layered protection is always the best choice.
EEK is descended from the magnificent A-Squared trojan hunter and that is still very much in its DNA. If you run into a problem that your AV can't fix, or if something detects and stops your AV from running, EEK is standing at the ready, and may very well fix the issue (it is one of the things I will use if you pay me to fix it for you).
In addition sommore, I will always recommend
CCleaner which, while technically not any sort of anti-virus or anti-spyware, is really pretty important wrt spyware and tracking...
CCleaner is a one-stop, one-push, trash dumping machine. It not only dumps your trash can, but also a myriad of other caches in your machine. Almost all tracking still defaults to cookies when other methods falter, so cleaning out the cookie jar is every bit as important as ever. And additionally many viruses and spyware set themselves up in your machine's temp directory (a place to download temporary files to), which CCleaner also empties every time you run it... which can in fact delete nasties in the doing of it.
All of these recommendations can be free to use, can be totally non-invasive, and can sit by waiting until you call them up manually - And I would highly recommend they are used that way... All you need is the discipline to sit down and run them from time to time, which can be a very peaceful and pleasant experience (see hot tea above)...
They will take a bit of setting up on installation, and I would be happy to help, if there is enough call for it...