Japanese media giant Nikkei Inc. has disclosed its third cybersecurity incident in about a month after attackers used stolen credentials to access a development system and expose 1.83 million personal information records stored in the cloud.
The company said the unauthorized access occurred during the early hours of October 7. Attackers reportedly used compromised credentials to enter a development system within Nikkei’s network, gaining access to information stored in a cloud environment. Nikkei disclosed the incident on October 16 and said it was still investigating the full scope of the exposure.
According to the company, approximately 150,000 records contained at least one type of personal information, including full names, email addresses, physical addresses, telephone numbers, or dates of birth. Around 120,000 records included email addresses. The remaining 1.68 million records contained identifiers that could not independently identify individuals. Nikkei confirmed that credit card information was not exposed.
Nikkei said it revoked the compromised credentials and reported the incident to Japan’s Personal Information Protection Commission on October 11. As of October 16, the company had found no evidence that the exposed information had been misused or published online. It also reported no signs of system compromise or data tampering resulting from the incident and said its services had not experienced any outages.
The company is continuing its investigation to determine how the credentials were stolen and the extent of the exposure. Nikkei said it would individually notify people whose information was affected and take additional steps to strengthen its security measures.
The latest incident follows two other cybersecurity disclosures involving employee accounts. Earlier in October, Nikkei revealed that attackers had accessed an employee’s Google Workspace account beginning in late July, potentially exposing personal information belonging to employees and business partners.
The company also disclosed that another employee’s Microsoft 365 account had been compromised in September. Attackers reportedly used the account to send approximately 9,000 phishing emails to people inside and outside the organization, including journalistic sources. The messages contained links to malicious websites and targeted individuals who had previously communicated with Nikkei employees.
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Nikkei has not publicly established whether the three incidents are connected or whether the same attackers were responsible. The repeated incidents nevertheless highlight the risks associated with stolen credentials, compromised employee accounts, and unauthorized access to cloud-based systems.
