seicomart-app-2026 · Disclosed First disclosure unknown
セイコーマート: unauthorized access and impact
Unauthorized access to the app server was confirmed; the method is withheld. 574,647 people’s data was accessed, revised from 572,022 in the third notice; members withdrawn by September 24 are excluded.
Outcome: Confirmed breach
Entry path and evidence
Timeline
Reviewed follow-up publication date; the first disclosure date remains unknown. [s1]
Reported response
- Reported fact
Members were notified of exposure status; online account-viewing and modification functions are being discontinued.
Evidence relevant to prevention
Insufficient evidence
Undisclosed entry or patch timing prevents an avoidability assessment. Inspect privileges, retrieval logs, retention and deployed configuration using the linked rules.
Editorial assessment; not a determination of liability. [s1]
Unknowns and AI involvement
The reviewed disclosures do not establish attacker use of AI.
The first disclosure date remains unverified. The company explicitly withholds the intrusion method.
Sources
[s1] セイコーマート · Primary source
セイコーマート：事故に関する公表資料 ↗Reviewed 2026-10-09
[s2] セイコーマート · Primary source
セイコーマート：事故に関する公表資料 ↗Reviewed 2026-10-09