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JAENES
ALeak confirmedNovember 5, 2026 announced

GMOペイメントサービスData breach / unauthorized access incident

笹尾 祐太朗の写真Reviewed by Yutaro SasaoWritten by Leak Watch editorial team published ・ updated
Occurred on
October 27, 2026
Announced on
November 5, 2026
Severity
AFinancial and HR records — information that easily translates into monetary damage.
Scale
106,997 records
Main impact
Due to unauthorized access to the email distribution service used by an outsourced provider, up to 106,997 pieces of personal information were leaked externally, of which up to 5,771 included billing-related information such as names, billed amounts, and billing details.
Information involved
Email addressFull name
Cause / key point
Unauthorized access to the shared environment of an external email distribution service allowed intruders to penetrate servers for client companies and extract information from the database.About Supply chain attacks (via vendors & shared services)
Industry
Finance & insurance
Listing / capital
Unlisted
Sources
Last updated
November 7, 2026

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Written & reviewed

笹尾 祐太朗の写真

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: 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 →

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