株式会社日建学院（事前確認講習システム） / （公財）マンション管理センターData breach / unauthorized access incident
- Occurred on
- Unconfirmed
- Announced on
- October 20, 2026
- Severity
- AFinancial and HR records — information that easily translates into monetary damage.
- Scale
- 3,597 people
- Main impact
- Personal information of 3,597 attendees of the preliminary confirmation training—names, addresses, phone numbers, email addresses, login IDs, etc.—may have been leaked externally. Credit card and bank account information are reported not to be included.
- Information involved
- Email addressUser / member IDPhone numberHome addressFull nameDate of birth
- Cause / key point
- Unauthorized access by a third party was confirmed, which may have resulted in personal information being leaked externally.
- Industry
- Education
- Listing / capital
- Unlisted
- Last updated
- October 21, 2026
Is this incident worth paying attention to?
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
Related incidents
Browse the database →Incidents sharing the same company, service, attack method or industry (grouped automatically from the disclosures).
Incidents related to "クレジットカード"
Incidents where the damage spread through the same service or system.
- SSリクルート（カーセンサーnet、C-MATCH）2026.10.21 announced・Affected 3,709,551 records
- Aニフティ（回線申込・受付管理システム）2026.10.19 announced・Affected 542,513 records
- Bデーリー東北新聞社（受注制作Webページ）2026.10.16 announced・Affected 423 records
- SSバーガーキング・ジャパン(公式アプリ)2026.10.15 announced・Affected 11,180,000 records
- SSソースネクスト2026.10.15 announced・Affected 22,519,960 records
- SSSアドベンチャー（スカイチケット）2026.10.10 announced・Affected 14,640,000 records
Same attack method
- SS焼肉きんぐ2026.10.05 announced・Affected 10,788,963 records
- Bユミルリンク（メール配信システム）2026.10.19 announced・Affected 9,000,000 records
- SSタイムズカー(タイムズモビリティ)2026.09.25 announced・Affected 6,600,000 accounts
- Sブックオフグループ(ブックオフコーポレーション)2026.10.09 announced・Affected 6,383,279 people
- Sヤマト運輸(クロネコ代金後払いサービス)2026.09.29 announced・Affected 5,310,000 records
- Aビューカード（VIEW’s NET）2026.10.09 announced・Affected 4,030,000 records
Same industry
- Sちとせグループ（ちとせアカデミー）2026.10.09 announced・Affected 843 people
- S山口大学（教職員メール）2026.10.06 announced・Affected 1 accounts
- S大阪公立大学2026.10.05 announced・Affected Unknown
- S日本エネルギー経済研究所2026.10.02 announced・Affected 13 records
- S日本原子力研究開発機構（研究支援サイト）2026.10.01 announced・Affected 175 people
- S大阪市立小学校（成長・肥満度曲線）2026.09.09 announced・Affected 18 people
Attack method classification: Unauthorized access (method undisclosed)(Breached, but the technique was not identified or disclosed)
Read the Unauthorized access (method undisclosed) guide and national trends →