岩井コスモ証券（委託先トレードワークス）Data breach / unauthorized access incident
- Occurred on
- Unconfirmed
- Announced on
- October 16, 2026
- Severity
- BIncidents centered on names and contact details.
- Scale
- 4,611 people
- Main impact
- Due to unauthorized access to a subcontractor, personal data including names and email addresses of 4,611 online trading users of 岩井コスモ証券 were leaked. No secondary damage had been confirmed at the time of disclosure.
- Information involved
- Email addressFull name
- Cause / key point
- The cause is under investigation.About Supply chain attacks (via vendors & shared services)
- Industry
- Finance & insurance
- Listing / capital
- UnlistedParent company: 岩井コスモホールディングス(東証プライム 8707)
岩井コスモ証券 is a subsidiary of 岩井コスモHD.
- Last updated
- October 20, 2026
Stock price reaction to the disclosure岩井コスモホールディングス・親会社 / 東証プライム 8707
Stock information is reference data based on Yahoo Finance and may be delayed. This site does not solicit or advise investment and does not guarantee the accuracy or completeness of this information. We accept no liability for any investment decision based on it.
Is this incident worth paying attention to?
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
Related incidents
Browse the database →Incidents sharing the same company, service, attack method or industry (grouped automatically from the disclosures).
Same attack method
- S第一興商（ビッグエコー等）2026.10.08 announced・Affected 8,631,000 records
- A旭化成セラピューティクス（Pharma DIGITAL）2026.10.06 announced・Affected 514,000 people
- A大和証券2026.10.05 announced・Affected 220,000 records
- CTOPPAN（損保ジャパン）2026.09.29 announced・Affected 177,426 people
- A大東ガス株式会社2026.09.28 announced・Affected 124,000 records
- A大阪大学2026.10.21 announced・Affected 77,851 people
Same industry
- Sアフラック生命保険2026.06.30 announced・Affected 4,400,000 people
- SCSアカウンティング株式会社2026.05.15 announced・Affected Unknown
- Sマネーフォワード（GitHub）2026.05.01 announced・Affected 370 records
- AFivot（IDARE）2026.10.13 announced・Affected 129,659 people
- Aビューカード（VIEW’s NET）2026.10.09 announced・Affected 4,030,000 records
- A損保ジャパン（SMILING ROAD）2026.10.07 announced・Affected 60,000 records
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 →