To date, Firefox has been affected by five vulnerabilities and IE 7 by six, according to Secunia's statistics.
Forty percent of the Firefox bugs remain unpatched, compared with 50 percent for IE 7. But only 13 percent of the Firefox bugs allowed system access, compared to 43 percent for IE 7, which is more closely integrated with Windows.
Correspondingly, Secunia ranked 17 percent of the IE bugs as "extremely critical," a status attained by none of the Firefox advisories.
Forty percent of the Firefox advisories were "highly critical", with the rest less serious. Along with IE 7's 17 percent "extremely critical" bugs, 33 percent were "highly critical" and the others were less serious.