A threat actor used a variety of infostealers to collect session information and access Claude accounts belonging to an unknown number of users.

Anthropic is warning some Claude users that infostealer malware on their PCs has stolen active Claude login sessions, allowing attackers to access accounts and consume their usage.

Anthropic is notifying Claude users about infostealer malware exploiting active login sessions, enabling attackers to access accounts and misuse usage limits.