Anthropic's Claude Mythos Preview identifies over 23,000 vulnerabilities in open-source projects with limited external review

Anthropic's Claude Mythos Preview analyzed 281 open-source projects and identified 23,019 candidate vulnerabilities. External security firms reviewed only 1,900 of these candidates, with maintainers receiving 1,596 reports and acknowledging 1,451 of them. As of May 22, 2026, 97 fixes were implemented upstream and 88 findings became published security advisories. The remaining 21,119 candidate vulnerabilities have not been reviewed by anyone outside Anthropic. Anthropic attributes this significant drop-off to a shortage of personnel available to verify the findings.