埼玉県警（アルカディア安否確認システム）Data breach / unauthorized access incident
- Occurred on
- October 13, 2026
- Announced on
- October 18, 2026
- Severity
- BIncidents centered on names and contact details.
- Scale
- 13,000 people
- Main impact
- 埼玉県警's disaster-status confirmation system had the names and personal email addresses of about 13,000 police officers and staff registered, and they were notified that these may have been leaked externally due to unauthorized access to a contractor’s cloud-based service. No personal information of non-police individuals is said to be registered, and no misuse has been confirmed.
- Information involved
- Email addressFull name
- Cause / key point
- Unauthorized access to the cloud-based safety confirmation service provided by アルカディア may have caused registered information to be leaked externally (cause under investigation).About Supply chain attacks (via vendors & shared services)
- Sources
- Last updated
- October 21, 2026
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).
Incidents related to "アルカディア"
Incidents where the damage spread through the same service or system.
- B栃木県警（アルカディア利用内部システム）2026.10.20 announced・Affected 3,900 people
- B伊万里・有田消防本部（NET119緊急通報システム）2026.10.15 announced・Affected 15 people
- B和歌山県立21校（ライデン・スクール）2026.10.15 announced・Affected 10,006 people
- A一宮市（アルカディア提供のメール配信・Net119等）2026.10.14 announced・Affected Unknown
- A斑鳩町（防災情報メール・ハザードン）2026.10.13 announced・Affected Unknown
- A箕面市（防災情報配信サービス）2026.10.13 announced・Affected Unknown
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
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 →