SHINDO2

Kashiwa City

Pupils84people

LEAK CONFIRMEDFull name / Profile fieldsMisdelivery · Closed (final report)

Open in the live monitor ▶
Disclosed
Jan 5, 2026
Leak
Leak confirmed
Type
Misdelivery
Status
Closed (final report)
Security spend
Not checked yet
Compensation
Not announced

What leaked

IdentityName
Account dataGrade and class

How many

  • Pupils 84 people

Who is affected

  • Pupils who entered the previous year's calligraphy exhibition

Cause

A document with pupils' personal data was attached by mistake to a calligraphy exhibition notice for parents

Timeline

  1. Wrong file attached when sending the calligraphy exhibition notice
  2. First disclosure

Response

  • Data deleted
  • Notified individuals

The error was noticed right after sending; the message was deleted so it could not be viewed in the app. Guardians were given an explanation and an apology

What you should do

  1. Check the company's notice to see if you're affected

Lessons for companies

  1. Use DLP: recipient checks, send delay, automatic attachment protection
  2. Report to the PPC: preliminary in 3–5 days, final in 30 (60 if malicious)
  3. Run red teaming and AI-assisted hardening, and publish how much you invest

Sources