Safari uses an external updater that only polls for updates at certain intervals. Microsoft's updates are distributed on the second Tuesday of the month. Those gaps in time between when a vulnerability is publicly disclosed and a person patches is crucial, as they're an open window for an attack.

The problem with lax patching falls squarely on the shoulders of the application vendors -- users often simply can't visually tell if their browser needs to be upgraded, Frei said.

He advocates software vendors take a cue from the food industry and put an "expiration date" right on top of the browser to let people know the browser's state. For example, a warning could appear beside the address bar: "145 days expired, three patches missing"

"It's a non-technical suggestion," Frei said. "How can you expect people that they run the update if they don't even know? We think it's the same as having a speed limit on a highway."

Even search engine companies such as Google could display the same warning above search results, as the browser version is transmitted to its servers when someone performs a query, Frei said.

Alternatively, security companies could make application version scanning part of their consumer products, which they have done for some enterprise-level software, Frei said.

But the problem of out-of-date browsers pales in comparison to the quagmire of plug-ins, which add extra functionality to the browser, such as Adobe's Flash and Apple's QuickTime multimedia program.

On average, people have between six to 10 plug-ins, many of which come from different vendors with different patching regimes and schedules, Frei said.

"The browser is the bread, and even if the bread is fine, if the ham is rotten, you have a problem," Frei said.

Just one software vulnerability in a plug-in can put a person's PC in danger. Frei is proposing that an organization such as a national Computer Emergency Response Team create a service where browsers can verify if it has the latest version of a plug-in.

Besides Frei, the study was also conducted by Thomas Dübendorfer of Google, Gunter Ollmann of IBM Internet Security Systems and Martin May from ETH. The study will be presented at the Defcon security conference next month in Las Vegas.