A (coverage-)guided fuzzer for dynamic language interpreters based on a custom intermediate language (“FuzzIL”) which can be mutated and translated to JavaScript.

Not an official Google project, but written and maintained by Google engineer Samuel Groß. The README lays out quite a bit on the concept, implementation, and usage of the fuzzer, but there’s even more to learn in this presentation from Offensive Con 2019 and the associated master’s thesis for which the project was produced.