---
title: 'Mitsui Sumitomo Insurance confirms Policyholder Page leak of about 37,000 records'
url: 'https://securteksecurity.com/news/mitsui-sumitomo-insurance-policyholder-page-breach-37000-records'
markdown: 'https://securteksecurity.com/news/mitsui-sumitomo-insurance-policyholder-page-breach-37000-records.md'
date: '2026-11-06'
description: 'Mitsui Sumitomo Insurance announced on November 6, 2026 that its investigation into unauthorized access to its Policyholder Page had confirmed a leak of approximately 37,000 customer records, including insurance policy numbers, names, addresses, phone numbers and email addresses. Credit card inform…'
taxonomy:
  category:
    - Breaches
  tag:
    - japan
    - finance
---

# [Mitsui Sumitomo Insurance confirms Policyholder Page leak of about 37,000 records](https://securteksecurity.com/news/mitsui-sumitomo-insurance-policyholder-page-breach-37000-records)

   6th Nov 2026   [japan](https://securteksecurity.com/tag:japan#body-wrapper) [finance](https://securteksecurity.com/tag:finance#body-wrapper)  

Mitsui Sumitomo Insurance announced on November 6, 2026 that its investigation into unauthorized access to its Policyholder Page had confirmed a leak of approximately 37,000 customer records, including insurance policy numbers, names, addresses, phone numbers and email addresses. Credit card information and bank account information were not included. The access was detected during the night of November 2, 2026, the related services were suspended late on November 3 and disconnected from the network, and the company says no unauthorized external access has occurred since the suspension and no misuse of the leaked information has been confirmed so far; affected customers will be contacted individually and a forensic investigation by an external agency is under way.

TBS News reports that the same round of announcements covers Mitsui Sumitomo's sister MS&AD insurers: Aioi Nissay Dowa Insurance and Mitsui Direct Insurance also confirmed leaks from their customer and quotation websites, bringing the three companies' combined total to over 710,000 records, with Aioi Nissay Dowa's leak including the last four digits of card numbers but no security codes. SecurTek tracks only Mitsui Sumitomo's own confirmed figure of about 37,000 records in the dashboard figures for this item, because the sister insurers' individual counts were not separately verified in this cycle; the item will be updated if their individual figures are confirmed.

Sources: [SmartScope](https://smartscope.blog/en/blog/mitsui-sumitomo-insurance-policyholder-page-unauthorized-access-confirms-2026/); [TBS News DIG](https://www.youtube.com/watch?v=ghKfv4qo828)

---

## Navigation

- Parent: [News](https://securteksecurity.com/news.md)
- Previous: [MIT and UBC WorldParticle: one AI model simulates sand, cloth, fluids and folding proteins](https://securteksecurity.com/news/mit-worldparticle-one-model-simulates-sand-cloth-fluids-proteins.md)
- Next: [Moldova government breach extracts data linked to about 750,000 people](https://securteksecurity.com/news/moldova-government-breach-data-linked-to-750000-people.md)