Researchers warned users not to open any unknown PDF files.
Researchers at security firm, FireEye, have discovered a zero-day security flaw in Adobe Reader, which is being exploited by hackers to launch sophisticated attacks.
FireEye researchers said, "We have found IE, Java, and Flash zero-days in a row in the past several months, and now it's PDF's turn."
"Today, we identified that a PDF zero-day 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.
"Upon successful exploitation, it will drop two DLLs. The first DLL shows a fake error message and opens a decoy PDF document, which is usually common in targeted attacks. The second DLL in turn drops the callback component, which talks to a remote domain."
FireEye says it has submitted the sample to the Adobe security team and urged users to not to open any unknown PDF files until it gets confirmation from Adobe and a mitigation plan is put in place.
Adobe said it is aware of reports that these vulnerabilities are being exploited and are designed to trick Windows users into clicking on a malicious PDF file delivered in an email message.
"Adobe is in the process of working on a fix for these issues and will update this advisory when a date for the fix has been determined," the company said.