Nikkei Says 17,000 Impacted by Data Breach Stemming From Slack Account Hack

Nikkei says 17,000 Slack users were affected by a data breach stemming from a Slack account hack, with compromised credentials enabling access to employee and business partner information. An investigation found that names, email addresses and chat histories belonging to over 17,000 Nikkei Slack users were compromised. The breach was discovered in September, and passwords have been changed as part of the incident response.

Nikkei noted that while the type of compromised information did not require disclosure to authorities, the company voluntarily reported the incident to Japan’s Personal Information Protection Commission. Infostealer malware has been known to collect Slack credentials from infected devices, and Hudson Rock reports that this type of malware has compromised more than 270,000 Slack credentials. The piece carrying the update was published on 5 November 2025 (6:24 AM ET). According to Nikkei, no leakage of information related to sources or reporting activities has been confirmed.