[lhnz]

Would the NSA be interested in knowing the security flaws of popular opensource programs that could be used for attacks?

Has the NSA ever used a 0day to access a machine they were interested in?

Are the people that work for the NSA likely to be smart enough to realise the NSA's upside in finding security flaws and not telling people about them?

Will the NSA have ever done a security review of popular opensource libraries?

I'm not begging the question. What we know is incomplete. However, answer those questions yourself and then imagine how you might answer those questions if you were rich, liked playing dirty, full of smart people, and in a position of power. That's as good a bet as any on what might have been going on.

My two cents: all that is needed is a small crack in security. I wouldn't bet on the internet being secure, because men and women are fallible and security is complex.