NLFSRs are intentionally designed/ used for cryptography to be highly "secure" and resistant to "weakness" aka finding their generating parameters _except_ through brute force. this is essentially the process of "cryptoanalysis/ decryption of a PRNG" which is studied extensively in cryptography. but there is at least one case study for consideration. the [KeeLoq](https://en.wikipedia.org/wiki/KeeLoq) code is based on a NLFSR and is used in a lot of automotive keylock systems, and therefore has been subject to heavy academic analysis/ experimental attacks. while some weaknesses have been found nevertheless it looks like most of the attacks are basically brute force, although there is some use of FPGAs to streamline the hardware attack. wikipedia notes Nicolas Courtois attacked KeeLoq using sliding and algebraic methods. see also [1]

[1] [Period, correlation and auto-correlation of non-linear feedback shift registers based sequences](https://crypto.stackexchange.com/questions/42594/period-correlation-and-auto-correlation-of-non-linear-feedback-shift-registers) / [Crypto stackexchange](https://crypto.stackexchange.com/)