SHINDO2

Sekibunkan Shoten

Email addresses320records

LEAK CONFIRMEDMisdelivery · Closed (final report)

Open in the live monitor ▶
Disclosed
Mar 19, 2026
Leak
Leak confirmed
Type
Misdelivery
Status
Closed (final report)
Security spend
Not checked yet
Compensation
Not announced

What leaked

ContactEmail address

Not leaked

  • No other personal data such as names, addresses or phone numbers

How many

  • Email addresses 320 records

Who is affected

  • Textbook customers

Cause

The sender put recipients in the CC field by mistake

Timeline

  1. Exposure began
  2. First disclosure

Response

  • Change process

BCC rule enforced, double checks before sending and a checklist for manual sends

What you should do

  1. Don't open links in emails from this company. The apology email itself may be fake
  2. 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