The conclusion of that brings up the "sandbox" which is supposed to be somewhat like running things in a form of virtual environment. But that also brings another point as well.
it runs Unite within a "sandboxed" environment, which should make it hard for people to jump from Unite into other parts of the PC's file system, but the company doesn't say what steps it's taking to prevent hacked PCs from misusing the service.
A company representative couldn't immediately comment for this story on Friday."
That also includes the link for the Faq page at Opera seen at Opera Unite frequently asked questions
One question there brings up the matter of security and cautions about providing any sensitive data.
At Opera, we take the security of your data very seriously, and we are very proud of our consistently solid reputation for security. Our experience in the Web browser industry enables us to know the risks and design our products to ensure that they are as safe and secure as possible for you to use.
Opera Unite services run in a very secure "sandbox", where only the files or folders you select can be accessed; nothing else on your computer is accessible. Be aware that when you share a folder on your computer, visitors can access all of the content contained in that folder, including sub-folders. If you do have any concerns, follow the tips in our Security and Privacy tutorial
, and, as a general rule, avoid sharing highly-sensitive personal or financial data."