Rebex products are not affected by the critical OpenSSL bug known as "Heartbleed". A Heartbleed exploit makes it possible for an attacker to access sensitive data such private keys used by the servers to encrypt SSL traffic, usernames and passwords.
This is not a design flaw in TLS/SSL protocol itself and only the popular OpenSSL library is affected. Rebex products that support TLS/SSL don't use OpenSSL, but a custom library written in C # with no unsafe code blocks, which means exploits based on buffer overruns are not even possible (unless there is a severe bug in .NET VM or one of the underlying Windows cryptographic libraries).
Use the Heartbleed checker at http://filippo.io/Heartbleed to check whether the websites or services you use are affected by the vulnerability.