Microsoft recently put out .NET Framework 3.5, and silently included a plug-in for Mozilla Firefox. In so doing, they have apparently exposed Firefox to a crapload of attack vectors that exploit Microsoft’s buggy code, bringing Firefox down to the same level of insecurity as Internet Explorer.
To make matters worse, that framework is not an optional install for most users of Windows — it will install automatically as a recommended installation, silently, without prompts, under the default Vista security settings, and the default under Windows XP once you’ve explicitly enabled automatic updates (which is strongly recommended in the installation process). If you can’t beat the competition at security, just bring them down to your level. That’s the way Microsoft innovates, I guess!