Microsoft researchers looked at a specific set of vulnerabilities that are found in applications on both Windows and Mac OS X and found that some attackers are going after flaws from as far back as 2009 in Office documents, and 2010 in Flash and Java and Reader. Researchers say this method of distribution allows the attacker to maximize their capability on multiple platforms. This highlights the importance of keeping security software up-to-date, and ensuring operating system and 3rd party security patches are installed (soon after they become available)
Source: https://threatpost.com/cross-platform-flaws-boon-attackers-073112/76864/