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JAENES
SPossible leakMay 13, 2026 announced

メディカ出版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
March 13, 2026
Announced on
May 13, 2026
Severity
SCompromise of deep personal data or usable credentials.
Scale
641,000 people
Main impact
Due to an internal unauthorized intrusion using a legitimate account, information of approximately 641,000 people (duplicates possible) may have been exposed; specific data items have not been disclosed.
Information involved
Auth token
Cause / key point
Intrusion into the internal network using legitimate account credentials.
Industry
Media & entertainment
Listing / capital
Unlisted
Sources
Last updated
October 20, 2026
Auth tokenHow severity is assessed →

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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: Unauthorized access (method undisclosed)(Breached, but the technique was not identified or disclosed)

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