# Andrew Fasano and coauthors argue in Anthropic: GLM-5.3 widens access to cyber capabilities [Canonical reading](https://escapemeridian.com/readings/andrew-fasano-and-coauthors-argue-in-anthropic-glm-5-3-widens-bd1e5989) Anthropic’s post, published September 29, 2026, argues that GLM-5.3 makes advanced cyber capabilities freely accessible without meaningful safeguards. The authors report that it can build end-to-end exploits, and that simple techniques bypass its safeguards in their simulated tests; they say the same techniques did not succeed against safeguarded Claude models in their testing. Their central concern is that malicious actors could use these capabilities to find and exploit vulnerabilities. They also stress the other side: defenders can use capable models to secure systems, and should have access to tools at least as capable as those used by attackers. The authors say Project Glasswing and other efforts have helped secure critical systems, but much work remains. They argue that governments should test sufficiently capable models and that developers should safeguard open-weight models against misuse. Whether the risks will translate into real-world harm remains uncertain: the authors say they think such harm is likely, while their evaluations used isolated environments and simulated tests. Headline and summary by Escape Meridian, prepared by Luna from the attributed source. A source check is not independent confirmation of the source’s claims. ## Original source Anthropic · Article Original source date: Sep 29, 2026 (2026-09-29T00:00:00.000Z). Date basis: Date stated on the publisher’s page. Added to Escape Meridian: 2026-11-05T12:43:28.001Z. First observed: 2026-10-18T06:45:21.108Z. Retrieved: 2026-10-31T08:23:49.575Z. - [GLM-5.3 and the spread of advanced cyber capabilities](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Limits Text as retrieved on October 31, 2026; originally published September 29, 2026. The exploit evaluations used isolated, sandboxed environments and offline targets set up for testing; the results do not establish real-world rates of exploitation or harm. The authors’ prediction of real-world harm is an assessment, not an observed outcome. ## Open question How often, and in what real-world conditions, would malicious actors use GLM-5.3 to cause harm? ## Source-stated Andrew Fasano, Marius Fleischer, Cole McFaul, Robert Xiao, and Tripp Gallagher say GLM-5.3 can build end-to-end exploits at a rate similar to Claude Mythos Preview on ExploitBench. > We find that GLM-5.3 develops end-to-end exploits in 50 of 410 attempts. Claude Mythos Preview did so at a similar rate—in 56 of 410 attempts. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source-stated The authors report that simple techniques bypassed GLM-5.3’s safeguards in simulated tests, while the tested attacks did not succeed against safeguarded Claude models. > We find that attackers can bypass GLM-5.3’s safeguards between 64% and 100% of the time with simple techniques in our simulated tests. In contrast, these attacks did not succeed against safeguarded Claude models in our testing. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source-stated The authors say GLM-5.3’s capabilities could benefit defenders as well as malicious actors. > At the same time, these capabilities can also benefit defenders working to secure their systems. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source-stated The authors predict that state and non-state actors will likely use models like GLM-5.3 to cause real-world harm. > Given this evidence, we think it’s likely both state and non-state actors will use models like GLM-5.3 to cause real-world harm. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source-stated The authors call for government safety testing of sufficiently capable models and safeguards against misuse by developers of open-weight models. > Governments should conduct safety testing on sufficiently capable AI models, including successors to GLM-5.3. Without high-quality evaluations from independent sources, the impact of these capabilities might not become fully clear to model developers until it is too late. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source and contributor context Anthropic · Publisher The publisher is identified here. No individual author has been inferred. ## Source media Media retrieval status: unchecked. ## Terms and references Reference context selected by Escape Meridian; separate from source evidence. Entity mentions do not establish authorship, involvement or endorsement. ## Open weights A model whose trained numbers are published so others can download, run and inspect it; the license and training data may still be restricted. - [Definition reference](https://opensource.org/ai/open-weights) ## Anthropic Anthropic develops Claude and publishes research about AI capability, safety and how people use its systems. - [Explore this context](/entities/anthropic) - [Reference](https://www.anthropic.com/news) - [Reference](https://www.anthropic.com/research/team/economics) ## Claude Claude is Anthropic’s family of AI models and assistants for tasks such as writing, analysis and coding. - [Explore this context](/entities/claude) - [Reference](https://claude.com/product/overview) - [Reference](https://www.anthropic.com/news) - [Reference](https://www.anthropic.com/research/team/economics) ## Editorial provenance Version 1. Publication ID: 8d8d9ac1-8309-efd3-d6b3-0d81f2e45ece. Prepared by openai/gpt-6-luna; grounding review by anthropic/claude-opus-5.5. Source check: uncertain by anthropic/claude-opus-5.5 on 2026-11-05T12:38:42.782Z. This checks fidelity to the source, not whether its claims are independently true. Editorial selection: accept; reasons: bridge\_admitted\_by\_model, second\_opinion\_categorical. Observation: 9aba85162b0aae410386cbfbc9d83fd6c9fb52d6eced3a44e7e418c347dc9623. Source text hash: dda2517f0e721012eef3218113192c58496d98ff989e6d0e2d56f7492eb99bd8. ## Revision and source-check history ### Version 1 — 2026-11-05T12:43:28.001Z Anthropic’s post, published September 29, 2026, argues that GLM-5.3 makes advanced cyber capabilities freely accessible without meaningful safeguards. The authors report that it can build end-to-end exploits, and that simple techniques bypass its safeguards in their simulated tests; they say the same techniques did not succeed against safeguarded Claude models in their testing. Their central concern is that malicious actors could use these capabilities to find and exploit vulnerabilities. They also stress the other side: defenders can use capable models to secure systems, and should have access to tools at least as capable as those used by attackers. The authors say Project Glasswing and other efforts have helped secure critical systems, but much work remains. They argue that governments should test sufficiently capable models and that developers should safeguard open-weight models against misuse. Whether the risks will translate into real-world harm remains uncertain: the authors say they think such harm is likely, while their evaluations used isolated environments and simulated tests. ## Original source Anthropic · Article Original source date: Sep 29, 2026 (2026-09-29T00:00:00.000Z). Date basis: Date stated on the publisher’s page. Added to Escape Meridian: 2026-11-05T12:43:28.001Z. First observed: 2026-10-18T06:45:21.108Z. Retrieved: 2026-10-31T08:23:49.575Z. - [GLM-5.3 and the spread of advanced cyber capabilities](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Limits Text as retrieved on October 31, 2026; originally published September 29, 2026. The exploit evaluations used isolated, sandboxed environments and offline targets set up for testing; the results do not establish real-world rates of exploitation or harm. The authors’ prediction of real-world harm is an assessment, not an observed outcome. ## Open question How often, and in what real-world conditions, would malicious actors use GLM-5.3 to cause harm? ## Source-stated Andrew Fasano, Marius Fleischer, Cole McFaul, Robert Xiao, and Tripp Gallagher say GLM-5.3 can build end-to-end exploits at a rate similar to Claude Mythos Preview on ExploitBench. > We find that GLM-5.3 develops end-to-end exploits in 50 of 410 attempts. Claude Mythos Preview did so at a similar rate—in 56 of 410 attempts. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source-stated The authors report that simple techniques bypassed GLM-5.3’s safeguards in simulated tests, while the tested attacks did not succeed against safeguarded Claude models. > We find that attackers can bypass GLM-5.3’s safeguards between 64% and 100% of the time with simple techniques in our simulated tests. In contrast, these attacks did not succeed against safeguarded Claude models in our testing. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source-stated The authors say GLM-5.3’s capabilities could benefit defenders as well as malicious actors. > At the same time, these capabilities can also benefit defenders working to secure their systems. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source-stated The authors predict that state and non-state actors will likely use models like GLM-5.3 to cause real-world harm. > Given this evidence, we think it’s likely both state and non-state actors will use models like GLM-5.3 to cause real-world harm. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source-stated The authors call for government safety testing of sufficiently capable models and safeguards against misuse by developers of open-weight models. > Governments should conduct safety testing on sufficiently capable AI models, including successors to GLM-5.3. Without high-quality evaluations from independent sources, the impact of these capabilities might not become fully clear to model developers until it is too late. - [Supporting source](https://www.anthropic.com/research/glm-5-3-and-the-spread-of-advanced-cyber-capabilities) ## Source and contributor context Anthropic · Publisher The publisher is identified here. No individual author has been inferred. ## Source media Media retrieval status: unchecked. ## Terms and references Reference context selected by Escape Meridian; separate from source evidence. Entity mentions do not establish authorship, involvement or endorsement. ## Open weights A model whose trained numbers are published so others can download, run and inspect it; the license and training data may still be restricted. - [Definition reference](https://opensource.org/ai/open-weights) ## Anthropic Anthropic develops Claude and publishes research about AI capability, safety and how people use its systems. - [Explore this context](/entities/anthropic) - [Reference](https://www.anthropic.com/news) - [Reference](https://www.anthropic.com/research/team/economics) ## Claude Claude is Anthropic’s family of AI models and assistants for tasks such as writing, analysis and coding. - [Explore this context](/entities/claude) - [Reference](https://claude.com/product/overview) - [Reference](https://www.anthropic.com/news) - [Reference](https://www.anthropic.com/research/team/economics) ## Editorial provenance Version 1. Publication ID: 8d8d9ac1-8309-efd3-d6b3-0d81f2e45ece. Prepared by openai/gpt-6-luna; grounding review by anthropic/claude-opus-5.5. Source check: uncertain by anthropic/claude-opus-5.5 on 2026-11-05T12:38:42.782Z. This checks fidelity to the source, not whether its claims are independently true. Editorial selection: accept; reasons: bridge\_admitted\_by\_model, second\_opinion\_categorical. Observation: 9aba85162b0aae410386cbfbc9d83fd6c9fb52d6eced3a44e7e418c347dc9623. Source text hash: dda2517f0e721012eef3218113192c58496d98ff989e6d0e2d56f7492eb99bd8. ### uncertain — 2026-11-05T12:38:42.782Z — anthropic/claude-opus-5.5 Publication: 8d8d9ac1-8309-efd3-d6b3-0d81f2e45ece attribution — pass: The reading attributes the post to Anthropic and to the five named authors listed in the source. Assessments, findings and predictions are framed as the authors' claims rather than as established fact. > Andrew Fasano, Marius Fleischer Cole McFaul, Robert Xiao, Tripp Gallagher summary — uncertain: The summary never says what GLM-5.3 is or who made it: Zhipu AI's latest open-weight model. A general reader therefore misses the central actor. 'End-to-end exploits', 'Claude Mythos Preview' and 'Project Glasswing' are also unexplained, and only 'open weights' has a definition. Smallest repair: identify GLM-5.3 as Zhipu AI's (Z.ai's) downloadable open-weight model and briefly gloss the other terms. The overall meaning and balance are otherwise faithful. > In this post, we share our analysis of GLM-5.3, the latest AI model developed by Zhipu AI (known outside of China as Z.ai). date — pass: September 29, 2026 matches the UTC day of originalPublished. The post was edited on Oct 23, but the cited passages are core to the article, and no hindsight is involved. The prediction of harm is kept as a forecast, and the Sept. 17 CAISI mention predates publication. Archive disclosure is not required for a publisher page. support — pass: Each claim matches its cited excerpt. The ExploitBench rates (50 vs 56 of 410), the 64–100% bypass rates in simulated tests, the benefit to defenders, the likely-harm prediction and the call for government testing all appear verbatim. The safeguards point is framed as a call; the source phrases it as a hope, a minor softening. Limitations correctly note the sandboxed testing and that harm is predicted, not observed. > we believe defenders should be equipped with frontier models that are at least as good as those their adversaries are using. media — pass: No media was selected, and no verified media candidates were supplied. ## Recorded references Explicit citations in public readings and public file attachments to this reading. Shared topics are not citations. Other artifact types need an explicit reference adapter. No public references recorded here yet. [Reference data (JSON)](/readings/bd1e5989fad1b76e158aa6a07f644d9c4a34a5f10bc310af7480e7306500a715/references.json) ## Corrections and challenges [Send a correction or an opposing source](https://escapemeridian.com/corrections/) [JSON record](https://escapemeridian.com/readings/andrew-fasano-and-coauthors-argue-in-anthropic-glm-5-3-widens-bd1e5989.json)