Polish scientists from Wroclaw University of Technology (thanks Neowin.net) have found a vulnerability in security technologies used across the Internet that may allow kleptographic attacks resulting in silent theft of information without user's awareness:

The attack is only possible if client application has been modified by a malicious person e.g. by infecting computer system by a virus or persuading a user to install a plug-in, download or compile modified code. Such application would not send any additional information and would act according to protocol specification but the data sent over secure channel would easily be disclosed only by sniffing network traffic. Probably all of the SSL/TLS and SSH protocols may be affected including Internet Explorer, Outlook Express, Mozilla Firefox, Mozilla Thunderbird and Opera.

There's no reason for panic. As long as the client app is secure then there's nothing to worry about...