I can't take this seriously at all. Just because the Firefox developers admit it when a bug is found and have it fixed within days, and Microsoft doesn't admit a bug exist untill there are exploits already taking over your pc before fixing doesnt mean firefox has more bugs.. It just means Firefox bugs are reported and fixed, while Internet Explorer Bugs are kept secret and only fixed when MS deems in necessary.
Yeah -- this is like concluding that Bush is sleazier than Clinton based on reports from the mainstream media (which tends to trumpet the former and downplay the latter).