Researchers from security firm FireEye claim that attackers are actively using a remote code execution exploit that works against the latest versions of Adobe Reader 9, 10 and 11. "Today, we identified that a PDF zero-day [vulnerability] is being exploited in the wild, and we observed successful exploitation on the latest Adobe PDF Reader 9.5.3, 10.1.5, and 11.0.1," the FireEye researchers said late Tuesday in a blog post.