三井不動産Data breach / unauthorized access incident
- Occurred on
- Unconfirmed
- Announced on
- September 1, 2026
- Severity
- SCompromise of deep personal data or usable credentials.
- Scale
- 19,000 records
- Main impact
- Up to 19,000 records of employees and related personnel and up to 36,000 records of external parties may have had names, email addresses, departments, etc. exposed; disclosure of email bodies, files, passwords, etc. has not been confirmed.
- Information involved
- Email addressFull name
- Cause / key point
- Unauthorized use of credentials for some systems.
- Industry
- Real estate
- Listing / capital
- Listed company東証プライム 8801(三井不動産)
- Last updated
- October 20, 2026
Stock price reaction to the disclosure三井不動産 / 東証プライム 8801
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Reviewed byYutaro SasaoFounder & CEO, MediaLeap Inc.
CEO of MediaLeap Inc. Working on both sides of web advertising and web media since 2013; founded the company in May 2025.
Review scope: cross-checking against primary sources (official and government announcements), verifying claims stay within the facts, and checking source attribution。Last reviewed:
Written by:Leak Watch editorial team (AI-assisted drafts verified against sources by the editorial team) · Reviewer profile · Request a correction
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Attack method classification: Under investigation / not stated(Cause not disclosed)
Read the Under investigation / not stated guide and national trends →