Joshin（社内ネットワーク）Data breach / unauthorized access incident
- Occurred on
- Unconfirmed
- Announced on
- October 17, 2026
- Severity
- AFinancial and HR records — information that easily translates into monetary damage.
- Scale
- Unknown
- Main impact
- Joshin has suspended some services due to unauthorized access to its internal network. Whether personal information was leaked is currently under investigation.
- Information involved
- Not specified in the disclosure
- Cause / key point
- The cause is under investigation.
- Industry
- IT & telecom
- Listing / capital
- Listed company東証プライム 8173(Joshin)
- Last updated
- October 20, 2026
Stock price reaction to the disclosureJoshin / 東証プライム 8173
Stock information is reference data based on Yahoo Finance and may be delayed. This site does not solicit or advise investment and does not guarantee the accuracy or completeness of this information. We accept no liability for any investment decision based on it.
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).
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
- 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
Same industry
- SSEストアー(ショップサーブ)2026.10.16 announced・Affected 23,356,000 people
- SSコミューン（Commune・Commune for Work）2026.10.09 announced・Affected 307,000 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
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 →