CKCネットワーク株式会社、株式会社学参Data breach / unauthorized access incident
- Occurred on
- May 2, 2026
- Announced on
- June 10, 2026
- Severity
- BIncidents centered on names and contact details.
- Scale
- 664,000 records
- Main impact
- Servers were affected by a ransomware attack; approximately 664,000 inquiry records (of which about 9,900 may include contact details) and about 53,000 member records were stored on the affected servers. No traces of external leakage have been confirmed to date, but a leak cannot be ruled out, and investigation and monitoring are ongoing.
- Information involved
- Email addressUser / member IDPhone numberHome addressFull name
- Cause / key point
- Unauthorized access by a third party exploiting a vulnerability in server management software, followed by ransomware infection.About Ransomware
- Industry
- Education
- Listing / capital
- Unlisted
- Last updated
- October 20, 2026
Is this incident worth paying attention to?
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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.
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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: Ransomware(Encrypting data and demanding a ransom)
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