Zhipu said its flagship GLM-5.3 model will be open-sourced at 10:00 a.m. Beijing time on Aug. 28, with model weights becoming available for download at that time. The company said GLM-5.3 had already gone live in Coding Plan on Aug. 14 and later opened API access, but the weight release came two weeks later for security reasons.
According to Zhipu, the model’s cybersecurity capabilities improved faster than expected during post-training. The company said the model not only became better at finding vulnerabilities, but also started to plan multi-step exploit chains, prompting internal security evaluation and hardening before the weights were released.
In Zhipu’s published benchmarks, GLM-5.3 scored 84.5% on the vulnerability-discovery test CyberGym, slightly above Mythos 5 at 83.8% and GPT-5.6 Sol at 83.6%. On ExploitBench, which focuses more on exploit execution, GLM-5.3 rose from GLM-5.2’s 24.4% to 54.4%, though it still trailed Mythos 5 at 78.0%. Zhipu also said the model found 2,436 vulnerabilities across 269 open-source projects, including 1,097 classified as critical or high severity.
Zhipu said its flagship GLM-5.3 model will be open-sourced at 10:00 a.m. Beijing time on Aug. 28, when the model weights will also become available for download.
The company said GLM-5.3 had already launched in Coding Plan on Aug. 14, followed by API access. The weight release came two weeks later.
Zhipu said the delay was tied to security. According to the company, GLM-5.3’s cybersecurity capabilities grew at a pace that was 「beyond expectations」 during post-training. It became better at finding vulnerabilities and also began to plan complete exploit chains across multiple steps. Zhipu said it carried out security evaluation and hardening before opening the weights.
Published benchmark results
In CyberGym, a vulnerability-discovery test, GLM-5.3 scored 84.5%, slightly ahead of Mythos 5 at 83.8% and GPT-5.6 Sol at 83.6%.
On ExploitBench, which is more focused on exploit execution, GLM-5.3 improved from 24.4% for GLM-5.2 to 54.4%, though it remained behind Mythos 5 at 78.0%.
Zhipu also said the model identified 2,436 vulnerabilities across 269 open-source projects, with 1,097 classified as critical or high severity.
The company said GLM-5.3 uses the same base model as GLM-5.2, and that all of the gains came from post-training.
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