Between late September and early October 2026, nine South Korean financial institutions suffered customer data leaks reportedly involving at least 65,000 personal and credit records, prompting a round-the-clock government cybersecurity emergency and a presidential order for a full investigation. A CrowdStrike report says the core tool was ARTEX, an open-source AI penetration-testing agent using models including DeepSeek, Claude Code and Grok and likely run by a single human operator — an assessment made with moderate confidence; damage hit peripheral systems rather than core clearing networks, with Shinhan Bank losing data on about 25,000 customers, while at least two banks reportedly repelled the same attack. ARTEX, built by a Chinese security engineer, appeared on GitHub in July 2026 and won Baidu's "agent+" challenge in August, and after disclosure its developer said on October 8 it would go closed source and disclaimed responsibility; the article also cites a late-September 2026 FTC probe of Anthropic and OpenAI and notes identified attack infrastructure was spread across the US (65.7% of IPs), China (14.8%) and Hong Kong (10.9%).