Multiple vulnerabilities have been announced for Apple Quicktime. I counted 11 different vulnerabilities in the advisory, ranging in criticality from disclosure of personal information to buffer overflows. Apple has released an update, version 7.4.5, that fixes these vulnerabilities.
Opera versions prior to 9.27 are vulnerable to multiple issues. These vulnerabilities could allow for the execution of code on the local host. Users should update to version 9.27.