Firefox to US$7,500 cash reward) to researchers who discover severe security holes in Firefox. Official guidelines for handling security vulnerabilities discourage early disclosure of vulnerabilities so as not to give potential attackers an advantage in creating exploits. Because Firefox generally has fewer publicly known security vulnerabilities than Internet Explorer (see "Comparison of web browsers"), improved security is often cited as a reason to switch from Internet Explorer to Firefox. "The Washington Post" reported that exploit code for known critical security vulnerabilities in Internet Explorer was available for 284 days in 2006. In comparison, exploit code for known, critical security vulnerabilities in
Firefox 4 time. Also on that date, the browser’s usage share was higher than all versions of Safari, Opera and older versions of Firefox with the exception of Firefox 3.6. As a reference, Internet Explorer 9’s usage share first exceeded that of Internet Explorer 6 on May 1, 2011 (48 days after release), and Internet Explorer 9 became the second most used version of Internet Explorer for the first time on May 22, 2011 (69 days after release). According to StatCounter, Firefox 4 reached its usage share peak of 16.7% on June 19, 2011. After that date, it started to decline due