Matsui Securities data breach
Matsui Securities announced a data breach on Nov 5, 2026 affecting about 830,000 email addresses, exposing email addresses. It happened through a vendor (Arara (email delivery service)). No settlement or compensation has been announced.
Was I affected?
Matsui Securities customers whose email addresses were used for its emails, such as Japanese stock and futures and options trading notices. Matsui says it will contact those affected.
| Announced | Nov 5, 2026 |
|---|---|
| When it happened | Intrusion at email vendor Arara, which reported the leak to Matsui on November 5, 2026; Matsui's own systems were not breached |
| Country | Japan |
| Email addresses exposed | 830,000 |
| Data exposed | Email addresses |
| Through a vendor | Arara (email delivery service) |
| Status | Confirmed by the company or a regulator filing |
What happened
Japanese online brokerage Matsui Securities said on November 5, 2026 that up to 830,000 customer email addresses leaked after an outsider broke into Arara, the company it used to send emails such as trading notices. Only email addresses were taken: login IDs, passwords, trading PINs, trade and asset details and withdrawal bank accounts were never given to Arara. Matsui says its own systems were not breached and urged customers to set up passkeys to guard against phishing.
What should I do?
- Don't sign in through links in emails that claim to come from Matsui Securities; use the official app or a bookmarked site.
- Set up a passkey for your Matsui account to make phishing harder.
- If you entered your login details or trading PIN on a fake site, change them at once and contact Matsui and the police.
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Sources
- 外部委託先への不正アクセスによるお客様のメールアドレス漏えいについて (Leak of customers' email addresses caused by unauthorized access at an outside contractor) · Matsui Securities (in Japanese) · official
- 松井証券 顧客のメールアドレス最大83万件漏えい · NHK (in Japanese) · news