The bug is in Android's WebView programming interface. Aside from giving attackers access to the devices' camera and file system via something as easy to set up as a booby-trapped web page, it can also be set off via a Man-in-the-Middle attack to deliver a trojanized app update which would then allow attackers to access all the things that the app itself has permission to use.
According to Ars Technica, the vulnerability in question was publicly disclosed in December 2012, and Google (finally!) fixed it in November 2013 when it released Android 4.2.
Tod Beardsley, technical lead for the Metasploit Framework, says that this vulnerability is "kind of a huge deal", and 70 percent of devices out there are vulnerable because they run Android versions below 4.2.
"In a completely unsurprising twist, I did a quick survey of the phones available today on the no-contract rack at a couple big-box stores, and every one that I saw were vulnerable out of the box," he added. "And yes, that's here in the U.S., not some far-away place like Moscow, Russia."
"I'm hopeful that by publishing an E-Z-2-Use Metasploit module that exploits it, we can maybe push some vendors toward ensuring that single-click vulnerabilities like this don't last for 93+ weeks in the wild," he concluded.
There is not much that users can do to fix this problem, except pester their carriers in great numbers in the hope that a security update will be released sooner rather than later, hope that cyber criminals won't start using the module en masse, and be careful on which links the click on when using their Android devices.
Users of devices who receive their OS updates directly from Google are safe, though.