Update 2: This exploit probably won't work on most Galaxy S III's as long as they have the most recent OTA update, as we demonstrate on video here.

Update: This issue is, unsurprisingly, a lot more nuanced than the video here lets on. The bug is based in the stock Android browser, is in fact quite old, and has been patched in more recent builds of Android - this is probably why Nexus devices running the most recent OTAs are unaffected.