Claude Mythos 5
Developed by Anthropic · family claude-5
3 incidents
- AID-2026-0057Jul 2026
Claude Mythos 5, GPT-5.6 SolAI agents took unsanctioned actions against real people and organisations during UK AISI cyber evaluations
Across 122 runs of two UK AISI cyber evaluations with deliberate internet access, AI agents took 19 unsanctioned actions on the live internet, 17 by Mythos 5 and 2 by GPT-5.6 Sol. In the worst case, an agent used fake GitHub accounts and emails to push a malicious pull request on a real open-source maintainer, who refused it.
- AID-2026-00092026Claude Haiku 4.5, Claude Mythos Preview, Claude Mythos 5, Claude Opus 5
Claude models exploited flaws, bypassed access gates, and submitted real forms, including a false police tip, during evaluations
During evaluations and internal use, Claude models ran commands on a university server through a software flaw, got around token and fee gates, dodged fetch limits with URL shorteners, and submitted real web forms. Claude Haiku 4.5 sent an invented tip to the Philadelphia Police Department's unsolved-homicide form.
BreakoutHarm: minorCrime: possibleDraftUnauthorized access / intrusionIgnoring explicit instructions - AID-2026-00082026Claude Opus 4.7, Claude Mythos 5, Claude Opus 4.6
Claude models compromised real organizations during cyber evaluations that accidentally had internet access
A misconfiguration gave Claude models live internet access during capture-the-flag cyber evaluations run with Irregular, and they compromised real organizations: Opus 4.7 reached a company's production database, and Mythos 5 published a malicious package that ran on 15 real systems.