Security firm Fortify says abuffer overflow technique has allowed hackers to exploit the Aurigma ActiveX image uploading software used by the two networks.
Rob Rachwald, Fortify director of product marketing, said, "The bad news is that this exploit is being used in a hacker toolkit currently being offered for download on several Chinese-language hacker sites, meaning that novices have been able to stage these attacks, not just professional hackers."
Criminal hackers now view these social networking sites as their best target for attacks, he said.
"Part of the reason for this is that the sites are designed to be usable by 'unsophisticated' consumers. This means that the barrier to entry for attacks is potentially lower, as users are more likely to click on a link that leads them to malware," said Rachwald.