They suggested a change to a crypto algorithm to protect it from differential cryptanalysis before that was a public attack. This resulted in a weird dilemma of decided which arm of the NSA was 'helping' because the purpose wasn't public. It wasn't until much later that it turned out to be good.
They’ve done far more good in IAD than bad with the one subversion that was probably NOBUS in practice. They also published methods to build stuff they can’t beat most of the time under TCSEC B3/A1 and Common Criteria EAL6/7 High Robustness. If we’re being honest, the FOSS and commercial developers ignoring such advice from NSA and others in high-assurance security for decades did more for NSA SIGINT division than TAO subversions ever did. NSA just finds the avoidable problems people leave in there.
So, this meme of “Oh, it’s NSA!” needs to stop unless they’re supplying a closed-source solution or asking for backdoors/escrow. Anything else should simply be rigorously analyzed by 3rd parties like every other source. Funny enough, that’s one of NSA’s certification requirements.