Anthropic Preemptively Secured Claude Accounts Hit by Infostealer Malware

Anthropic detected stolen Claude session cookies traced to infostealer malware on users' own machines and forced sign-outs, deleted stored payment cards, and refunded unauthorized charges — without waiting for users to report the abuse. Six commodity malware families were blamed. Anthropic's infrastructure was not breached. The number of affected users was not disclosed.