Hi Barry,
Sebastian is right (as usual). Despite the many, many (many!) public DotNetNuke installations out there, with all the myriad configurations, I am aware of only two that have been hit with the nihaorr1 injection. Both of these are virtually certainly affected via third-party modules and cross-application contamination. Of those two pathways of infection, the latter is the overwhelmingly more likely to be the cause.
The real morale of the story here: move your weak legacy ASP.NET applications to DotNetNuke, and you no longer have to worry about this particularly insidious injector!
Sebastian: I know you require all-SPs to pass the release process. However, I recall seeing the use of the EXEC statement in a couple of these SPs (I believe I logged one of them in Gemini). As this could be a backdoor avenue of infection, have you considered disallowing this particular statement from SPs that go through the release process?
Brandon