About eight out of every 10 Web browsers run by consumers are vulnerable to attack by exploits of already patched bugs, according to a security expert.
The poor state of browser patching stunned Wolfgang Kandek, CTO of security risk and compliance management provider Qualys, which presented data from the company's free BrowserCheck service Wednesday at the RSA Conference in San Francisco.
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"I really thought it would be lower," said Kandek of the nearly 80 percent of browsers that lacked one or more patches.
BrowserCheck scans Windows, Mac, and Linux machines for vulnerable browsers, as well as up to 18 browser plug-ins, including Adobe's Flash and Reader, Oracle's Java and Microsoft's Silverlight and Windows Media Player.
When browsers and their plug-ins are tabulated together, between 90 percent and 65 percent of all consumer systems scanned with BrowserCheck since June 2010 reported at least one out-of-date component, depending on the month. In January 2011, about 80 percent of the machines were vulnerable.
Even worse, about 30 percent of browser plug-ins are perpetually unpatched, a rate triple that of Windows, where Qualys' data has shown that, on average, about 10 percent of all PCs never receive Microsoft's patches.
When plug-ins were excluded, browsers fared better: Only about 25 percent of the scanned machines had an unpatched browser on board last month.
Kandek read those results as proof that browser updates were applied more regularly by users. "The lower percentage shows that updating works pretty well for [browsers]," he said.
Unlike most plug-ins, browsers either silently self update -- as does Google's Chrome -- or automatically check for new patches, a practice of Microsoft's Internet Explorer (IE) and Mozilla's Firefox.
The most likely plug-in to require a patch is Oracle's Java, which was outdated on more than 40 percent of the scanned systems. Adobe's Reader was second, with about 32 percent of the computers reporting a vulnerable version. Apple's QuickTime took third, with less than 25 percent.
Java was also in the top spot last year when Qualys unveiled statistics from BrowserCheck's first three months of operation.
"I bet that most people don't even know that they have Java, or how it installs," said Kandek. "Exploit writers have recognized that, and have been adding Java exploits in their toolkits."
Although Oracle usually releases Java updates quarterly, last week it rushed out an emergency patch to quash a critical bug.
Kandek said he sees two solutions.