Double whammy for CACert.org users
If you are using OpenSSL (or ever did use it with any of your current keypairs in the last 3-4 years), you are probably in a rush to upgrade all your systems and replace all your private keys right now.
If your certificate authority is CACert.org then there is an extra surprise in store for you. CACert.org has changed their hash to SHA-512 recently and some client/server connections silently fail to authenticate with this hash. Any replacement certificates you obtain from CACert.org today are likely to be signed using the new hash. Amongst other things, if you use CACert.org as the CA for a distributed LDAP authentication system, you will find users unable to log in until you upgrade all SSL client code or change all clients to trust an alternative root.