The algorithm is open ... however it was produced by a politically motivated rogue government branch that seems to harbouring a cynical bunch of criminal bastards ... do your own due diligence, if you don't have to deal with them why bother?
Don't forget that the Internet and TOR were also started by the US military.
Just the fact that they did something does not mean that they still have control over it.
Edit: oops, forgot to point out that the NSA algos flaws/backdoors will be tailored towards cracking by hardware capabilities that they , and maybe only them, possess. So saying it is secure because no-one else has found a flaw is redundant since no-one else knows or can replicate what they are capable of in terms of mining the exploit ...
Flaws in one of most widely used algos would be quickly found by NSA's/USA enemies - such as China and Russia (Russia/China have some of the world brightest mathematicans & cryptographers).
Especially after the Prism scandal.
Hiding something like this is simply not possible in after-Prism paranoia world.