Fuso Dentsu: a shared folder in the cloud storage it uses with outside parties was accessed without authorization, and 26,489 personal data records may have leaked

1. 2026-07-15

   It confirmed unauthorized access to a shared folder in the cloud storage it uses to share information with outside parties. [3]

2. 2026-07-22

   It announced the unauthorized access (first report). [2]

3. 2026-09-10

   In the second report it announced the findings. A third party misused credentials; the route by which they were obtained was not identified. The folder held files with personal data, and 26,489 records (names, addresses and phone numbers) of customers and contacts of its business partners may have leaked. [1] [3]

No payment-related data such as bank account numbers or card data was included, and no secondary damage such as misuse of the data has been found. It is contacting the people affected individually. [1]

As prevention, it will require multi-factor authentication for outside users of the cloud storage, tighten its password policy, review its rules for externally shared folders and audit accounts twice a year. [1]