MIXI（コトポータル）Data breach / unauthorized access incident
- Occurred on
- October 5, 2026
- Announced on
- October 14, 2026
- Severity
- AFinancial and HR records — information that easily translates into monetary damage.
- Scale
- 750 people
- Main impact
- Profiles and related data of 750 コトポータル members may have been viewed or obtained, of which 749 included email addresses. There is no evidence that this incident affected コトダマン main accounts or payment information.
- Information involved
- Email addressUser / member ID
- Cause / key point
- A third party exploited multiple vulnerabilities in コミューン's system, and this is not attributed to MIXI's configuration or operational shortcomings. コミューン says it has fixed the vulnerabilities and blocked the access routes.
- Industry
- IT & telecom
- Listing / capital
- Listed company東証プライム 2121(MIXI)
- Last updated
- October 20, 2026
Stock price reaction to the disclosureMIXI / 東証プライム 2121
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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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Attack method classification: Under investigation / not stated(Cause not disclosed)
Read the Under investigation / not stated guide and national trends →