コミューン（Commune・Commune for Work）Data breach / unauthorized access incident
- Occurred on
- October 5, 2026
- Announced on
- October 9, 2026
- Severity
- SSLarge-scale compromise of sensitive data such as payment or identity-verification records affecting millions.
- Scale
- 307,000 people
- Main impact
- Unauthorized access impersonating an administrator resulted in leakage of an estimated 30.7万人 of member information, confirmed data overwrites, and unauthorized password changes for 144 people. Multiple communities were affected.
- Information involved
- Email addressUser / member ID
- Cause / key point
- Unauthorized access exploiting a system flaw.
- Industry
- IT & telecom
- Listing / capital
- Unlisted
- Last updated
- October 20, 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
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Incidents related to "コミューン"
Incidents where the damage spread through the same service or system.
Same attack method
- SSソースネクスト2026.10.15 announced・Affected 22,519,960 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
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- 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
Same industry
- SSEストアー(ショップサーブ)2026.10.16 announced・Affected 23,356,000 people
- SSIDCフロンティア（IDCFクラウド）2026.10.07 announced・Affected 48 records
- SS楽天ドライブ2026.10.06 announced・Affected 15,382 accounts
- SSHelpfeel（Gyazo）2026.09.16 announced・Affected 23,620,000 records
- SPingCAP2026.10.21 announced・Affected 50,000 people
- S日本電気株式会社2026.10.20 announced・Affected Unknown
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 →