Yahoo has begun warning individual users that their accounts may have been compromised in a massive data breach it reported last year. A forged cookie may have allowed hackers to gain access to Yahoo accounts without passwords. Yahoo has not identified the state-sponsored actor responsible for the breach. The company recommended that users review their accounts for suspicious activity, be cautious of unsolicited communications that ask for personal information, and avoid clicking on links or downloading attachments from suspicious email messages. Yahoo: “We continuously enhance our safeguards and systems that detect and prevent unauthorized access to user accounts””]