Heartbleed is a flaw in the OpenSSL protocol (which is not used by 3dcart). OpenSSL is an open-source encryption technology which is the backbone for many secure websites that collect personal and financial data. Fortunately, OpenSSL is not used on any 3dcart web properties. You can learn more about the Heartbleed Bug here.
Heartbleed has been present since March 2012, but has only recently been identified. While your 3dcart stores have not been impacted in any way by this vulnerability, it is recommended that watch for communication from different websites and companies that you may have frequently visited in the event that these companies were using the OpenSSL technology. Many major websites such as Amazon, Google, Facebook and others may have been impacted.
To learn more about how to protect yourself from the Heartbleed Bug, we suggest reading this article from CNET.
As always, we appreciate your business here at 3dcart, and we are always here to help.