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Announcements<br>Project Glasswing: An initial update<br>May 22, 2026
Last month, we launched Project Glasswing, our collaborative effort to secure the world’s most critical software before increasingly capable AI models can be turned against it.<br>Since then, we and our approximately 50 partners have used Claude Mythos Preview to find more than ten thousand high- or critical-severity vulnerabilities across the most systemically important software in the world. Progress on software security used to be limited by how quickly we could find new vulnerabilities. Now it’s limited by how quickly we can verify, disclose, and patch the large numbers of vulnerabilities found by AI.<br>In this post, we discuss what we’ve learned about this critical challenge for cybersecurity in the first weeks of Project Glasswing. We focus on the early public evidence of Mythos Preview’s performance, on the initial results of our effort to scan thousands of open-source software projects, and on what this progress means for cyberdefenders today. We also cover what to expect next from Project Glasswing, and how we’re thinking about releasing Mythos-class models in the future.<br>Our early results<br>Our approach to discussing Mythos Preview’s findings<br>The software industry’s longstanding convention is to disclose new vulnerabilities 90 days after they’re discovered (or, if a patch is created before the 90 days is up, around 45 days after the patch becomes available). This allows time for end users to update their software before a vulnerability can be exploited by attackers. Our own Coordinated Vulnerability Disclosure policy takes this approach.<br>However, this means that disclosed vulnerabilities are a lagging indicator of the accelerating frontier of AI models’ cyber capabilities: we’re not yet at the point where we can fully detail our partners’ findings with Mythos Preview without putting end users at risk. Instead, we provide illustrative examples of the model’s performance, along with aggregate statistics on our progress to date. Once patches for the vulnerabilities that Mythos Preview has discovered are widely deployed, we’ll provide much more detail about what we’ve learned.<br>Evidence from our partners and external testers<br>Project Glasswing’s initial partners build and maintain software that is fundamental to the functioning of the internet and other essential infrastructure. Fixing flaws in their code reduces risk for the many other organizations that rely on it, and therefore reduces risk for billions of end users.<br>After one month, most partners have each found hundreds of critical- or high-severity vulnerabilities in their software. Collectively, they’ve found more than tens thousand. Several have told us that their rate of bug-finding has increased by more than a factor of ten. For instance, Cloudflare has found 2,000 bugs (400 of which are high- or critical-severity) across their critical-path systems, with a false positive rate that Cloudflare’s team considers better than human testers.<br>This tallies with external testers’ experience of Mythos Preview’s performance, and with recent additional evaluations of the model:<br>The UK’s AI Security Institute reports that Mythos Preview is the first model to solve both of their cyber ranges (simulations of multistep cyberattacks) end to end;<br>Mozilla found and fixed 271 vulnerabilities in Firefox 150 while testing Mythos Preview—over ten times more than they found in Firefox 148 with Claude Opus 4.6;<br>XBOW , an independent security platform, reports that Mythos Preview is a “significant step up over all existing models” on its web exploit benchmark, and provides “absolutely unprecedented precision” on a token-for-token basis;<br>ExploitBench and ExploitGym , two recently released academic benchmarks for measuring models’ exploit development capabilities, show Mythos Preview as the strongest performer. We discuss what these benchmarks tell us about the model in more detail on our Frontier Red Team blog.<br>More generally, we’re now seeing that patched software is being rolled out much more quickly. The latest Palo Alto Networks release included over five times as many patches as usual. Microsoft has reported that the number of new patches they’ll release will “continue trending larger for some time.” And Oracle is finding and fixing vulnerabilities across its products and cloud multiple times faster than before.<br>Mythos Preview has also proved useful for other kinds of security work. For example, at one of our Glasswing partner banks, Mythos Preview helped to detect and prevent a fraudulent $1.5 million wire transfer after a threat actor compromised a customer’s email account and made spoof phone calls.<br>Open-source software<br>For the last few months, Anthropic has used Mythos Preview to scan more than 1,000 open-source projects, which collectively underpin much of the internet—and much of our own infrastructure.<br>So far, Mythos Preview has found what it estimates are 6,202 high- or critical-severity...