GLM-5.3 Nearly Matches Anthropic Model in Cyber Exploit Tests

Z.ai’s open-weight GLM-5.3 developed end-to-end cyber exploits at rates approaching those of the restricted Claude Mythos Preview, highlighting the security implications of widely distributed model weights. GLM-5.3 produced working exploits in 50 of 410 ExploitBench attempts, compared with 56 successful attempts for Claude Mythos Preview. On an internal binary-exploitation benchmark, GLM-5.3 achieved full control-flow hijacks in 4% of 100 randomly selected trials, while Anthropic’s model reached 6%. The National Institute of Standards and Technology’s Center for AI Standards and Innovation ranked GLM-5.3 as the most cyber-capable open-weight model released or evaluated to date. Its aggregate cyber capability trailed the U.S.

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