An unauthorized group gained access to Anthropic's Mythos AI model, a cybersecurity tool designed for enterprise use, through a compromised third-party vendor account on the same day it was publicly announced. Anthropic is investigating but says there's no evidence their own systems were compromised by the breach. The group, apparently interested in exploring unreleased AI models rather than causing damage, provided Bloomberg with screenshots and live demonstrations proving they had access. This matters because Mythos was intentionally released only to select vendors like Apple specifically to prevent unauthorized access to a tool Anthropic itself describes as potentially dangerous in the wrong hands.