How security researchers used Anthropic to hack OpenAI

· Thestack · Sept. 18, 2026, 3:20 p.m.
Summary
This blog post discusses a newly identified vulnerability related to Anthropic's Claude Opus 5 and its connection to a poor Single Sign-On (SSO) implementation that security researchers exploited to hack OpenAI. The author shares insights on the implications of this vulnerability and how such scenarios can occur.