How one hacker used AI agents and a few thousand dollars to break into scores of sites

Researcher Fagerland found about two dozen instances of an open-source AI problem-solving platform called Cairn being used for malicious activity, according to a report provided to Reuters ahead of publication on Monday. Reuters reported the findings on October 19, 2026, in an article titled 'How one hacker used AI agents and a few thousand dollars to break into scores of sites.' The article describes a single individual using AI agents to conduct intrusions against scores of sites at a cost of a few thousand dollars.

Fagerland characterized the find as real-life evidence that commercially available AI agents could pull off complex intrusions from start to finish without human intervention, the report said. Cairn is described as open-source and as an AI problem-solving platform. The report places the number of observed malicious uses at about two dozen and the cost of the operation at a few thousand dollars. The article's headline attributes the activity to one hacker and puts the number of affected sites at scores.

The stated significance of the finding is that commercially sold agentic software can execute the sequence of a complex intrusion end to end, rather than assisting a human at individual steps. Reuters published the account on Monday, October 19, 2026. Both the count of malicious uses and the cost estimate originate in the report provided to Reuters ahead of publication.