media4u-account-list-2026 · Disclosed 2026-07-14
メディア4u: unauthorized access and impact
Unauthorized access to the SMS delivery service exposed account-management information; initial entry is undisclosed. Of 95,412 management-list records, 22,928 may contain personal data. One client account sent 280 unauthorized messages; authentication secrets were excluded.
Outcome: Confirmed breach
Entry path and evidence
- Reported fact
Unauthorized access to the SMS delivery service exposed account-management information; initial entry is undisclosed.
[s1]7月17日第二報 §§1-4 / FAQ - Reported fact
Of 95,412 management-list records, 22,928 may contain personal data. One client account sent 280 unauthorized messages; authentication secrets were excluded.
[s1]7月17日第二報 §§1-4 / FAQ
Timeline
Disclosure date established by the reviewed notice. [s1]
Reported response
- Reported fact
Access was blocked, administrative credentials revoked and reissued, vulnerabilities fixed, and monitoring strengthened.
Cause and mitigation hypotheses
Not assessed. Editorial hypotheses have not been added for this incident; this does not establish safety or a confirmed cause.
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 initial entry route, attack start and complete extraction scope are undisclosed. Management-list records are not all confirmed personal-data records.
Sources
[s1] メディア4u · Primary source
メディア4u：事故に関する公表資料 ↗Reviewed 2026-10-09
[s2] メディア4u · Primary source
メディア4u：事故に関する公表資料 ↗Reviewed 2026-10-09