According to this post on the official V8 Javascript blog, the pseudo-random number generator (PRNG) that V8 Javascript uses in Math.random() is horribly flawed and getting replaced with something … ...

The method used to generate the digits, a pair of 555 timers sending pulses through linear-feedback shift registers, would at best be considered pseudo-random.

Over the years, multiple studies have found that Google Chrome’s V8 JavaScript engine was returning not-so-random numbers when you called the Math.random() function. Today that’s been fixed ...

That means that even if some enemy understands everything about how the random number generator works, they still can’t predict the outcome.

Current methods of generating random numbers can produce predictable results. Researchers said the new method could generate higher-quality random numbers with less computer processing.