Investigating

Mitsui Fudosan: credential misuse on used systems may have exposed staff and external-contact data

Unauthorized access to some systems confirmed Aug 28, 2026. Credential misuse may have exposed up to ~19k staff records and ~36k external email contacts; disclosed Sep 1. Business files/passwords not confirmed leaked.

Last updated: 2026-11-09

Overview

“Up to” category figures are not stored/summed → blank.

Timeline

  1. Occurred
  2. Discovered
  3. Disclosed

Organization response

Per the notice, the organisation investigated and contained the incident, notified individuals and offered monitoring or protective resources.

What you can do

Be wary of emails, SMS or calls impersonating the organisation; do not open links or attachments or enter passwords or card details. Change reused passwords on other services.

Sources

  1. 不正アクセスによる情報漏えいの可能性について三井不動産株式会社 · 2026-11-09

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