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Anthropic locks out Claude users after infostealers hijack login sessions

Anthropic invalidated Claude sessions compromised by infostealers such as Vidar, Lumma and Atomic Stealer, which steal browser cookies to bypass 2FA.

Anthropic began locking users out of Claude accounts after infostealer malware stole browser session cookies, letting attackers replay logins and bypass two-factor authentication. Identified malware includes Vidar, Lumma (LummaC2), StealC, RedLine and Acreed on Windows and Atomic Stealer (AMOS) on a small number of Macs. Anthropic signed affected users out, removed saved payment methods and refunded unauthorized charges. One affected user traced the infection to a pirated game downloaded from a Russian underground forum; the company advised victims to remove the malware before resetting passwords and re-enabling 2FA.

Help Net Security · 15d agoData breach in the wild1

Week in review: Records allegedly stolen from Azure tenants, Medusa ransomware hits 500+ orgs

Week in review: Medusa ransomware hit 500+ orgs per CISA, millions of Azure tenant records allegedly stolen, SafePal and French tax authority breaches disclosed.

Help Net Security's weekly roundup covers the FBI, CISA, and HHS joint advisory update reporting Medusa ransomware has breached more than 500 organizations since June 2021, and threat actor TheHatman's claim of millions of employee records stolen from Azure tenants of Fortune 500 firms including McDonald's, Vodafone, Kyndryl, and Tata Consultancy Services, per Hudson Rock. It also covers the SafePal breach affecting 39,798 customers, France's DGFiP breach exposing data on 678,000 individuals, and UT San delaying its fall semester after a cyberattack. Security items include critical unauthenticated GitLab flaw CVE-2026-19478, an actively exploited patched macOS Screen Sharing flaw deploying a cryptominer, US charges against 17 Mabna Institute Iranian hackers over 31TB of stolen academic data, and Google Mandiant's AI agents finding 100+ high-severity vulnerabilities.

Help Net Security · 23d agoData breach in the wildCVE-2026-19478