I wouldn’t say this work is novel in the general case of “PRNGs are not CSPRNGs”. You can throw a constraint solver at most any PRNG and given sufficient output determine the state fairly easily. As a datapoint, doing this for xoroshiro took me half an hour: https://gist.github.com/karanlyons/805dbcc9e898dbd17e06f2627...

Heh, that sounds cool. I'll save opening that link for later.

Don’t worry, it’s safe: I didn’t put the actual solver, just proof that I solved it. Wouldn’t want to spoil the fun for anyone else :)

I made no comment on the work done here, it is novel and concerning if you use the outputs for important things. My comment is that non-cryptographic random number generators should not be used for security-critical functions.

These functions are specifically built for speed, not security.