ちとせグループ（ちとせアカデミー）Data breach / unauthorized access incident
- Occurred on
- Unconfirmed
- Announced on
- October 9, 2026
- Severity
- SCompromise of deep personal data or usable credentials.
- Scale
- 843 people
- Main impact
- Unauthorized use of one administrator account was confirmed. Up to 843 people’s names, emails, profiles, etc. may have been leaked, and the acquisition of member passwords has been denied.
- Information involved
- Email addressUser / member IDFull name
- Cause / key point
- Unauthorized access to contractor Commune.About Supply chain attacks (via vendors & shared services)
- Industry
- Education
- Listing / capital
- Unlisted
Education business of ちとせグループ.
- 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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Same industry
- S山口大学（教職員メール）2026.10.06 announced・Affected 1 accounts
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Attack method classification: Supply chain attacks (via vendors & shared services)(Compromising the provider instead of the user)
Read the Supply chain attacks (via vendors & shared services) guide and national trends →