Those vulnerable sites included domains owned by Google, Facebook, Microsoft, and Symantec, all of which the researchers contacted to alert the companies to the new Web bug.

FORBES: Researchers Say Hijackable Bug Infects 30% Of Websites

On its TechNet Web site, Microsoft refers to the bug as the "Web Server Folder Traversal" vulnerability.

CNN: Microsoft servers hit by another hacker

The tool takes advantage of cross-site scripting, a common bug in Web sites that takes control of a user's browser when he or she clicks on a specially crafted link, or in some cases, simply visits a compromised page.

FORBES: Magazine Article

Microsoft has released a temporary software fix for a newly discovered bug in its Internet Explorer web browser.

BBC: Microsoft warns on previously unseen IE bug

Though the current bug has been patched, Oberheide says Web bugs like the one he found are too common for Google to allow installation of phone apps from the Web without warning.

FORBES: Android Bug Would Have Allowed Phone Infections From A Computer Click

Semmelhack, a tall, tousle-haired and confidently cerebral Web veteran, says it would be inapt to compare the Bug to mass-market gadgets like the iPhone.

FORBES: Bug Labs is going after the long tail of gadgetry