GLM-5.3 matches Mythos on flaw detection but trails badly on weaponizing exploits

pstAsiatech · x · 2026-08-19

GLM-5.3 scored 84.5% on CyberGym (reading code, finding and confirming security flaws), slightly ahead of Mythos 5's reported 83.8%. But the gap widens sharply on turning flaws into working exploits: 54.4% on ExploitBench vs 78.0%, and 105 timed attack-development tasks in two hours vs 181.

The author notes Mythos was initially touted as a defensive cyber tool; Anthropic turned it into a potent offensive capability through a sophisticated harness and agentic platform — it's not just the model, but full-stack engineering and cyber-operations knowledge.

Related event: GLM-5.3 Cyber Eval Released as Z.ai Restricts Offensive Capabilities(2 posts)→

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