Facebook has admitted to a security breach on its systems but reassured users that no data was at risk from the attack.
The company said on Friday that last month several of its employee notebooks were infected with malware from a zero-day attack on a third-party website. While Facebook did not provide details on the specific site, it said that the employees picked up the malware from a mobile phone developer's site.
After detecting the malware through suspicious activity on its networks, Facebook said that it tracked down the infected systems and discovered that the malware had been delivered through a Java exploit.
"The compromised website hosted an exploit which then allowed malware to be installed on these employee laptops. The laptops were fully-patched and running up-to-date antivirus software," Facebook said in a post to its security blog.
"As soon as we discovered the presence of the malware, we remediated all infected machines, informed law enforcement, and began a significant investigation that continues to this day."
Facebook said that the compromised systems were fixed and Oracle has since issued an update to address the Java vulnerability.
The Facebook employees are not alone in falling victim to a Java exploit. Experts believe that the platform is the most popular online attack target in the world.
Facebook did not say whether the use of Java was necessary for the jobs of the employees, but security experts have advised that, whenever possible, Java browser plug-ins should be disabled by users and administrators to help prevent attacks.