Since it's such an old report, it's most likely referring to Dual_EC_DRBG: https://en.wikipedia.org/wiki/Dual_EC_DRBG

So don't read the article as being about Unifi currently being backdoored by the NSA, but that the USG3 was one of the products using the Cavium/Marvell chips with the flaw that were being used globally in 2013 when the Snowden archive was released.