A day after reports that attackers are exploiting a zero-day vulnerability in Microsoft's Internet Explorer browser, researchers warned of a separate active campaign that was targeting a critical vulnerability in fully patched versions of Adobe's ubiquitous Flash media player.

The attacks were hosted on the Syrian Ministry of Justice website at hxxp://jpic.gov.sy and were detected on seven computers located in Syria, leading to theories that the campaign targeted dissidents complaining about the government of President Bashar al-Assad, according to a blog post published Monday by researchers from antivirus provider Kaspersky Lab. The attacks exploited a previously unknown vulnerability in Flash when people used the Firefox browser to access a booby-trapped page. The attackers appear to be unrelated to those reported on Sunday who exploited a critical security bug in Internet Explorer, a Kaspersky representative told Ars.

While the exploit Kaspersky observed attacked only computers running Microsoft Windows, the underlying flaw, which is formally categorized as CVE-2014-1776 and resides in a Flash component known as the Pixel Bender, is present in the Adobe application built for OS X and Linux machines as well. Adobe has updated all three versions to plug the hole. Because security holes frequently become much more widely exploited in the hours or days after they are disclosed, people on all three platforms should update as soon as possible. People using IE 10 and 11 on Windowws 8 will receive the update automatically, as will users of Google's Chrome browser. It can sometimes take hours for the automatic updates to arrive. Those who are truly cautious should consider manually installing them. Windows users with Firefox installed must run a separate update for both IE and the Mozilla browser.

Kaspersky Lab researcher Vyacheslav Zakorzhevsky said the attacks were carried out in two separate exploits and were detected as early as April 9 by a general heuristic signature in the company's AV network. Both of the SWF files are able to bypass security mitigations built in to Flash and Microsoft Windows, including Windows 8, he said. One of the exploits, embedded in a file titled include.swf, is designed to target computers that have the Cisco Systems MeetingPlace Express Add-In version 5x0 installed. The app is used to view documents and images during Web conferences.

"We are sure that all these tricks were used in order to carry out malicious activity against a very specific group of users without attracting the attention of security solutions," Zakorzhevsky wrote. "We believe that the Cisco add-in mentioned above may be used to download/implement the payload as well as to spy directly on the infected computer."

He continued:

When we entered the site, the installed malware payloads were already missing from the "_css" folder. We presume the criminals created a folder whose name doesn’t look out of place on an administration resource and where they loaded the exploits. The victims were probably redirected to the exploits using a frame or a script located at the site. To date, April 28, the number of detections by our products has exceeded 30. They were detected on the computers of seven unique users, all of them in Syria, which is not surprising considering the nature of the site. Interestingly, all the attacked users entered the website using various versions of Mozilla Firefox. It’s likely that the attack was carefully planned and that professionals of a pretty high caliber were behind it. The use of professionally written 0-day exploits that were used to infect a single resource testifies to this. Moreover, while the first exploit is pretty standard and can infect practically any unprotected computer, the second exploit (include.swf) only functions properly on computers where Adobe Flash Player 10 ActiveX and Cisco MeetingPlace Express Add-In are installed. The Flash Player Pixel Bender component, which Adobe no longer supports, was used as the attack vector. The authors were counting on the developers not finding a vulnerability in that component and that the exploit would remain active for longer. All this suggests that the attackers were not targeting users en masse.

The exploitation of critical vulnerabilities by state-sponsored or state-motivated adversaries has grown increasingly common in recent years. Most notable examples include the Stuxnet Flame , and Red October malware campaigns. A raft of other smaller campaigns have regularly targeted the Macs and Windows PCs belonging to dissidents of China and other countries as well as private companies and government agencies , although many such attacks don't rely on previously unknown vulnerabilities in widely used products.