Summary Project Zero compared two automated tools used by Google to find vulnerabilities in Chrome’s JavaScript engine, V8, on a regular basis. Fuzzilli is a generative JavaScript engine fuzzer and BigSleep is an LLM-based bug finding system. In the past six months, BigSleep found more vulnerabilities than Fuzzilli (45 versus 37) with a 25% overlap in the specific bugs reported. Since this comparison methodology has a tendency to underestimate overlap, we also performed dedicated experiments to test theoretical overlap in vulnerabilities reported since 2023. These experiments estimated overlap at roughly 60%. Regardless of which value is accurate, a substantial portion of vulnerabilities wer