Germany warned users on Friday after malicious code - implicated in attacks on Google - was published online.
But Microsoft told BBC News that IE8 was the "most secure browser on the market" and people should upgrade.
PC could become infected with a "trojan horse", allowing a hacker to take control of the computer and potentially steal sensitive information.
Patch path
But Mr Evans said that calls to change browsers were "not very helpful".
"If you look at other browsers, it's likely they will have other vulnerabilities," he said.
He pointed to a report by security firm NSS Labs reportedly showing that IE8 provided better security against phishing and malware than other browsers.
"We feel strongly that IE8 is most secure browser on the market," Mr Evans said.
Source: BBC World News
