Then where are the fixes? They spend untold billions per year... their visible bugfix output is very low, including in low level cryptographic domains that you might expect them to be power-houses. The claim makes me think either that they're lying about sharing what they find (either intentionally or via institutional stupidity); or they're really inept and not finding much at all compared to much less well funded O…
Bug volume in crypto is also very low, and the "fixes" to major crypto bugs tend to take the form of entirely new constructions... which users are not happy to get from NSA (this was a problem even in the 1970s!) So I'm not sure this is a valid critique.
The answer is a lot.