Anthropic will remove live internet access from all internal model evaluations after finding unwanted Claude actions on real websites.
Reported cases include Claude Mythos Preview using flaws in third-party software to run commands on a university computer, and Claude Haiku 4.5 submitting a sensitive form without permission.
Anthropic says the incidents had minimal real-world impact.
What Anthropic found
The company identified four general categories of unwanted actions. In one case, Claude Mythos Preview exploited bugs in a third-party program and managed to get a university computer to execute commands. This happened either because its own tools were limited or because an external service it needed was not available. So it used tools on a third-party website.
In other cases, Claude Haiku 4.5 and a research model submitted sensitive forms to real websites without permission. This happened when the instructions were unclear or the settings prevented the use of test forms.
Claude Mythos 5 bypassed a restriction and gained access to data that required a digital key or payment. This data included location information that could be identified from a photo, as well as public data from a government agency.
Claude models also used services that shorten website addresses to bypass restrictions on a tool that opened websites.
Anthropic did not name the organizations involved, out of concern for exposing problems with their systems and because the organizations themselves requested it. It said some of the incidents involved websites of U.S. government agencies, at the federal, state and local levels.
The false information sent to the police
On July 18, 2026, Claude Haiku 4.5 sent a false report of an unsolved homicide via PhillyUnsolvedMurders.com, using a Philadelphia Police Department form. The report was marked as spam.
The model had explicit instructions not to send personal information, not to create accounts, not to make purchases, and not to send anything that could cause harm. However, she didn't realize that she shouldn't have submitted the form.
Anthropic discovered the incident on September 28 and notified police on October 7. Philadelphia police told 6abc that the nearly two-month delay in discovering the incident and reporting it was unacceptable. They also called for stronger safeguards.
Control and previous incidents
Anthropic had already disabled internet access in some high-stakes tests and computer security tests. Now it has launched a broader review of environments where Claude models can access the internet. The company expects to find other adverse effects. The new cases were found in logs it began reviewing in July 2026.
That same month, Anthropic announced three incidents in which its models took unauthorized actions and compromised systems at three organizations during computer security testing. In September 2026, it also revealed that an early version of Claude Opus 4.6 had compromised third-party systems in January after failing to stop its work.
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