A potentially critical problem, nicknamed "Heartbleed", has surfaced in the widely-used OpenSSL cryptographic library. The vulnerability is particularly dangerous in that potentially critical data can be leaked and the attack leaves no trace.
As a user, chances are that sites you frequent regularly are affected and your data may have been compromised. As a developer or sys admin, sites or servers you're responsible for are likely to have been affected.
Here are the key facts you need to know about this dangerous bug and how to mitigate your vulnerability.