opera -- XMLHttpRequest security bypass

A Secunia Advisory reports:

Secunia Research has discovered a vulnerability in Opera,
which can be exploited by malicious people to steal
content or to perform actions on other web sites with the
privileges of the user.
Normally, it should not be possible for the
XMLHttpRequest object to access resources
from outside the domain of which the object was
opened. However, due to insufficient validation of server
side redirects, it is possible to circumvent this
restriction.