Opera reports:
If a malicious page redirects Opera to a specially crafted
address (URL), it can cause Opera to crash. Given sufficient
address content, the crash could cause execution of code
controlled by the attacking page.
Once a Java applet has been cached, if a page can predict the
cache path for that applet, it can load the applet from the
cache, causing it to run in the context of the local machine.
This allows it to read other cache files on the computer or
perform other normally more restrictive actions. These files
could contain sensitive information, which could then be sent
to the attacker.