156 CVEs in Firefox this year compared to 133 in Chrome. Worse, but not ‘nowhere near up to par’.
https://plus.google.com/u/0/+JustinSchuh/posts/CNEgtJWYTb5
http://lcamtuf.blogspot.com/2010/05/vulnerability-databases-...
Why? Surely as with any software one should only install extensions that one trusts?