There's no cat and mouse -- they agreed to this blocking. I have in fact encouraged them to use a different extension ID if and when they make a fixed ClickOnce/WPF add-on that can be installed by active user choice rather than by default!

MS09-054 is labelled as an Internet Explorer update, so it's not obvious that Firefox users need to apply it. We're working with Microsoft on getting that fixed. Microsoft did definitely agree to it; I'm the one they told, on the telephone, before I requested the block be pushed out. I don't know why you think I was lying -- I didn't "imply" it, I flat out said that they agreed, which is the case. Do I have a history of lying about such things?

See http://blog.mozilla.com/security/2009/07/19/milw0rm-9158-stack-overflow-crash-not-exploitable-cve-2009-2479/ for more details, including specifics about how the bug affects different platforms and versions (worst case: unexploitable crash in OS X system libraries).