Anthropic recently forced logged out many Claude users and removed payment methods due to a large-scale account security incident. Hackers used malware like Vidar and Lumma to steal session cookies, bypassing 2FA and passwords to hijack accounts. The focus shifted from stealing bank cards to harvesting expensive AI computing power and API quotas, which are monetized via shell websites or proxy API platforms. Anthropic took decisive action by revoking sessions and deleting credit cards. Users are advised to manually log out of all devices, clear browser cookies, and avoid unofficial software downloads to protect their digital assets.