Mon Apr 28, 2014 3:37pm EDT

(Reuters) - Adobe Systems Inc released an update on Monday to its widely used Flash Player software to fix a bug that cybersecurity company Kaspersky Lab said had been exploited to attack visitors to a Syrian government website.

Adobe said in an advisory posted on its security website that the vulnerability could allow attackers to gain control of affected computer systems. It released updates to fix the bug for systems running on Microsoft Corp's Windows, Apple Inc's Mac and Linux operating systems.

Moscow-based Kaspersky Lab said on its blog that it learned in mid-April that a Syrian Justice Ministry website, jpic.gov.sy,

that serves as an online forum for citizen complaints had been compromised. No attacks on other websites have been reported as a result of the Flash bug.

"We believe the attack was designed to target Syrian dissidents complaining about the government," Kaspersky Lab researcher Vyacheslav Zakorzhevsky said in the blog post.

Kaspersky described the attack as a "watering-hole" campaign. In such attacks, hackers infect websites frequented by individuals whose computers they are looking to compromise. When they visit the tainted site, their systems become infected.

(Reporting by Jim Finkle in Boston; Editing by Richard Valdmanis and Lisa Shumaker)