The company said in a blog post the incident occurred in January and involved an early version of Claude Opus 4.6. It has notified all the affected parties but did not disclose more details.

Anthropic discloses a fourth security incident involving Claude Opus 4.6, including a January 2026 breach that exposed 150 GB of Mexican

Sept 9 : Anthropic on Wednesday identified a fourth cybersecurity incident involving an early version of its Claude AI model, a month after disclosing that the chatbot had hacked…