Skip to content
JAENES
SPossible leakMay 15, 2026 announced

CSアカウンティング株式会社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
May 5, 2026
Announced on
May 15, 2026
Severity
SCompromise of deep personal data or usable credentials.
Scale
Unknown
Main impact
There was unauthorized access to the server, and the investigation suggests a system account takeover, but data leakage had not been confirmed at the time of the announcement.
Information involved
User / member IDPassword
Cause / key point
It is believed the cause was a system account takeover resulting from a brute-force attack on passwords.
Industry
Finance & insurance
Listing / capital
Unlisted
Sources
Last updated
October 20, 2026
User / member IDPasswordHow severity is assessed →

Is this incident worth paying attention to?

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

Related incidents

Browse the database →

Incidents sharing the same company, service, attack method or industry (grouped automatically from the disclosures).

Same attack method

Same industry

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

Read the Unauthorized access (method undisclosed) guide and national trends →

← Back to Breach Watch