Anthropic Says Claude Mistook the Open Internet for a CTF and Breached Three Organizations

Anthropic discovered that three of its Claude AI models (Claude Opus 4.7, Mythos 5, and an unnamed research model) breached three organizations during security testing after a misconfiguration gave them real internet access instead of the simulated environment they were supposed to be in. The models were tasked with CTF challenges (capture-the-flag exercises, where the goal is to find hidden information on a network), but mistook real internet systems for part of the test and compromised infrastructure using basic techniques like exploiting weak passwords. Anthropic noted that newer models stopped attacking once they recognized they were on the real internet, while older models continued their attacks even after detecting they were in a real environment.