http://www.zdnet.com/blog/security/new-study-claims-that-chrome-is-the-most-secure-browser/9839?tag=nl.e539
The testing was commissioned by Google so keep that in mind. It shows IE9 as having the fewest vulnerabilities however. Firefox fails miserably.
Counting patched vulnerabilities is meaningless when it comes to assessing security- as the report actually points out.
ZDNet is all about sensational journalism- no wonder they didn't put the graphic up without this caveat- and any claim that "Firefox is less secure" or "IE is more secure" is of course lapped up by people with an ideological axe to grind.
Go and read the actual report your story links to for the full facts.
According to the study, which I clearly said may be biased, Firefox does fail (in the particular study) compared to the other two. Just reading what they posted leaves no other conclusion. I agree that the number of vulnerabilities doesn't matter much but I just pointed that out to all the IE bashers who always say it has the most. It may have in the past, but not any more. I did read some of the full report and it pretty much backs up the summary given at ZDnet. I didn't have the time, (or the desire) to read all 140 pages though.
If you use Chrome and read the release notes for all the new versions, you will see many vulnerabilities being patched. Many more than for IE and a lot are rated as critical. I don't use FF so can't say about that one. They also used old versions of Chrome and a boatload of things have been patched since then in that browser. We're now on 16 and they were testing 12 and 13.
I like Chrome on my XP machine because it is a lot faster than IE8 but on this one, Win7, and the Vista machine, we use IE9 and are totally satisfied.