Ironically, Firefox also released 3.0.5 to address critical security flaws.
Actually there is nothing ironic about it at all - The firefox fixes are unrelated to the Microsoft exploit.
What’s New in Firefox 3.0.5
One of the things I like. Firefox bugs are usually fixed proactively (There are no widespread exploits).
Microsoft bugs are often fixed reactively - as damage control.
At least to the credit of Microsoft, they did announce when the problem seemed to be getting worse, that users should use an alternative browser. To fail to do this and keep it "quiet" until a patch was ready - would be very wrong.
As a side note - with Mozilla, you can review the status of any issue or bug that is being worked on - you can read discussions between the developers, the reasons behind some decisions, you can send messages or suggestions - everything is entirely open - you can email the developer who is working on your fix etc. When was the last time you were able to read a Microsoft developers notes and see the progress of the resolution of a bug you are waiting on? Can you see how a particular fix was tested? As interested as you want to be, you can be involved in the future of Firefox. With Microsoft, apart from putting your suggestion into the feedback box and hoping that someone reads it - anything beyond that is "confidential" and you might get to see what they are doing when the next beta gets released to everyone.