西武鉄道（52席の至福）Data breach / unauthorized access incident
- Occurred on
- January 9, 2025
- Announced on
- September 2, 2026
- Severity
- SCompromise of deep personal data or usable credentials.
- Scale
- 500 people
- Main impact
- Approximately 500 people's names, contact details, and reservation-related information became externally viewable; of these, about 30 included considerations such as allergies and wheelchair use. It has been confirmed that the data were in a viewable state.
- Information involved
- Email addressUser / member IDFull nameHealth & medical data
- Cause / key point
- Misconfiguration during the implementation of the reservation site's information-sharing feature.
- Industry
- Transport & travel
- Listing / capital
- UnlistedParent company: 西武ホールディングス(東証プライム 9024)
西武鉄道 is a subsidiary of 西武ホールディングス.
- Last updated
- October 20, 2026
Stock price reaction to the disclosure西武ホールディングス・親会社 / 東証プライム 9024
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Written & reviewed
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: Misconfiguration & access-control gaps(Data left readable by anyone)
Read the Misconfiguration & access-control gaps guide and national trends →