Overview
The vendor reported 625,429 email addresses, of which 31,333 include optional birth date, gender, prefecture and similar fields (a subset). The cause was given as a web-server vulnerability in the vendor environment. Per the company, this stems from unauthorised access to the Arara email-delivery platform (recorded separately); this figure is a subset of the vendor scope and must not be added to it.
Timeline
- Occurred
- Discovered
- Disclosed
Organization response
Suspended newsletter sign-ups and delivery.
What you can do
Be wary of emails, SMS or calls impersonating the organisation; do not open links or attachments or enter passwords or card details. Change reused passwords on other services.
Sources
- 委託先のメール配信サービスへの不正アクセスによる個人情報漏えいに関するお詫びとご報告株式会社モンテローザ · 2026-11-09