ローソン（メールサーバー）Data breach / unauthorized access incident
- Occurred on
- September 25, 2026
- Announced on
- October 1, 2026
- Severity
- BIncidents centered on names and contact details.
- Scale
- 700,000 records
- Main impact
- The mail server was abused, and an estimated 700,000 suspicious English-language emails were sent. Information leakage, data-center intrusion/tampering, and malware infection were not confirmed at the time of disclosure.
- Information involved
- Email address
- Cause / key point
- Cause under investigation.
- Industry
- Retail & e-commerce
- Listing / capital
- UnlistedParent company: KDDI(東証プライム 9433)
ローソン was delisted in 2024. KDDI and 三菱商事 are joint investors.
- Last updated
- October 20, 2026
Stock price reaction to the disclosureKDDI・親会社 / 東証プライム 9433
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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 →