The bug, which is not strictly a security vulnerability but actually part of the PDF specification, was by Belgium researcher Didier Stevens last week. Stevens demonstrated how a multistage attack using the PDF specification's "/Launch" function could successfully exploit a fully-patched copy of Adobe Reader.

Unlike other attacks based on rogue PDFs, Stevens' technique does not require an underlying vulnerability in Adobe's Reader or Acrobat, but instead relies on social engineering tactics to dupe users into opening a malicious PDF. In his demo, Stevens used a PDF document containing attack code that he was then able to execute using the /Launch function. Although Reader and Acrobat display a warning when an executable inside a PDF file is launched, Stevens found a way to partially modify the alert to further trick a potential victim into approving the action.

It will be easy for hackers to replicate Stevens' strategy, said Mickey Boodaei, CEO of security company Trusteer, best known for Rapport, a security service that helps online banks, brokerages, and retailers secure customers' desktops.

"Didier's information is very clear, very easy to reproduce, and the attack seems to be very effective," said Boodaei. Although Stevens did not release proof-of-concept attack code, Trusteer's engineers were easily able to duplicate his attack, including the modifications to Reader's and Acrobat's warnings.

Boodaei assumes that criminals will be able to replicate the attack -- within days, if they haven't already -- and believes that they will immediately add it to the already-in-place multi-exploit kits that they've hidden on compromised legitimate sites.