---
title: Unauthorized access to Seicomart app may have exposed personal information of about 570,000 accounts
url: https://www.dataloco.com/en/unauthorized-access-to-seicomart-app-may-have-exposed-personal-information-of-about-570000-accounts
published: 2026-10-01T18:20:29+00:00
language: en
section: Security
source: https://ascii.jp/elem/000/004/437/4437907/?rss
publisher: Dataloco
---

# Unauthorized access to Seicomart app may have exposed personal information of about 570,000 accounts

On September 29, an unauthorized access incident was reported regarding the Seicomart smartphone application, potentially compromising the personal information of Seicomart Club members. The number of user IDs that may have been affected is approximately 570,000 accounts.

The personal data that may have been accessed includes full names, gender, date of birth, addresses, phone numbers, email addresses, and the dates of club card membership and cancellation. Passwords were not leaked, and the company stated that it does not hold credit card information.

The issue began with a suspicious cancellation process of a club card detected on September 24 between 22:00 and 23:00. Subsequent investigations revealed that unauthorized access to the server holding member information might have occurred shortly after 17:00 on September 28. No other accounts have been confirmed to have undergone unauthorized cancellations.

The company halted connections to the affected server at 20:00 on the same day. Functions such as new memberships, changes to member information or registered cards, cancellations, and logins to my page have been suspended. Currently, no fraudulent use of the electronic payment system known as Peko Mama money has been confirmed.

Seicomart is urging customers to be cautious of emails that appear to be from the company. Investigations into the cause of the incident and measures to prevent recurrence are ongoing, and findings will be disclosed on the official website and social media as they become available.

## This story in other languages

- [Français](https://www.dataloco.com/fr/intrusion-detectee-sur-lapplication-seicomart-pres-de-570-000-comptes-compromises)