Z.ai announced GLM 5.3 on Friday, Aug. 14, 2026, introducing an open-weight artificial intelligence model built for advanced coding and cybersecurity work. The company said the model runs on the same base architecture as its predecessor, GLM 5.2, with every capability gain coming from expanded post-training instead of a larger base model. Z.ai launched OpenVuln alongside the release, a scanning service, branded internally as "VulnHunter," that uses GLM 5.3 to check public code repositories for security flaws. Maintainers submit projects for review, and Z.ai publishes an aggregate security score while keeping detailed findings private until a fix is ready. On CyberGym, a benchmark that scores how well a model finds known vulnerabilities in source code, GLM 5.3 reached 84.5 percent, up from 77.2 percent for GLM 5.2. On ExploitBench, a separate benchmark measuring exploit reasoning, the new model scored 54.4 percent, more than double GLM 5.2's 24.4 percent. Both figures come from Z.ai's own testing and have not been independently verified. Z.ai's public disclosure ledger credits GLM 5.3 with 2,436 vulnerability findings across 269 open-source projects, including 1,097 rated critical or high severity. The company said several of those flaws turned up in the Linux kernel and in widely used VMware and Apache projects. A Z.ai developer advocate also wrote on X that GLM 5.3 flagged a possible vulnerability in Cursor, the AI coding tool SpaceX acquired earlier this year. Z.ai said it will hold back GLM 5.3's public model weights for about two weeks after the Aug. 14 launch, restricting access during that window to a group of vetted security partners through its GLM Coding Plan and ZCode agent. In its announcement, Z.ai wrote that the model's gains "can help defenders identify weaknesses earlier, validate risks, and accelerate remediation." The company also acknowledged that those same gains carry risk