CMU benchmark shows Claude Mythos outperforms GPT-5.5 at autonomous browser exploitation
claude mythos preview achieved human-level autonomy in exploiting real-world v8 vulnerabilities in cmu's exploitbench benchmark, significantly outperforming openai's gpt-5.5 despite costing $36k versus $3k.
carnegie mellon university's exploitbench evaluates agents on a five-tier scale up to arbitrary code execution within google's v8 javascript engine. claude mythos preview performed comparably to a competent human security researcher, successfully exploiting vulnerabilities like cve-2024-0519 that humans failed to crack for a year. in fully autonomous mode, mythos maintained high performance with a 9.55 score, whereas gpt-5.5 dropped to 4.30. despite the capability gap, the economic barrier remains steep, with mythos requiring twelve times the compute cost of its competitor. anthropic and openai provided api credits for the independent study.