Google Chrome ranked 21st on Secunia's list of top 50 applications at the end point. The company issued 28 advisories in 2012, repairing 291 vulnerabilities, Secunia said. Google repairs flaws quickly using an automated update mechanism and employs a silent update feature that can download a security update in the background while it is being used. The update is applied when the browser is closed and reopened by the end user. Chrome's malware block rate varied from 13 percent to just more than 74 percent, according to testing by NSS Labs in 2012. The testing firm found Chrome also blocked only 1.6 percent of click fraud attempts.