A critical flaw has been patched by the Opera team, the same day in which Secunia reported it existed. The Secunia advisory warned of a JavaScript flaw in version 9 of the Opera browser, one bad enough to earn the "Critical" rating and having the potential to result in system compromise.

What makes the fix actually interesting, however, is how the Opera team discovered the flaw. It was done through to use of a recently released tool that the Mozilla corporation made available:

Fortunately, Opera already knew about the problem and on Wednesday released a more secure version of Opera, version 9.23. How did it know? The Norwegian browser company said it used a tool that was released during this year's Black Hat USA by rival Mozilla, the makers of the Firefox browser.
That is somewhat surprising, and shows some very quick adoption rates to the tool Mozilla is offering. Perhaps Microsoft is tinkering with the tool as well? If you are using the Opera browser, you should upgrade to 9.23 today.