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Matsui Securities
Tokyo, Japan2 sources
Confirmed:Confirmed by the organisation, a regulator or a securities filing. First reported 5 Nov 2026.
Matsui Securities confirms up to 830 thousand email addresses leaked via AraRa
Matsui Securities confirmed that customer email addresses were leaked via the AraRa email distribution service. Up to 830,000 records were potentially exposed.
- Type
- Data breach
- Sector
- Finance
- Records
- 830K records confirmed
- First reported
- 5 Nov 2026
- Latest source
- 5 Nov 2026
What to do
- If you have an account, change that password, and anywhere you reused it.
- Turn on two-factor authentication, ideally an authenticator app or passkey, not SMS.
- Expect phishing that uses your real details. Do not click links in messages about this incident; go to the company's site directly.
- If payment cards were involved, watch statements and ask your bank for a new card.
- If government ID or social security numbers were involved, consider a credit freeze.
- If this is a vendor of yours, ask what of your data they held and whether it was in scope.
- Reset any API keys, SSO trusts or shared credentials you have with them.
- Brief your help desk: attackers often impersonate the breached brand next.
Not sure? Ask an assistant with the sources attached, or have a coding agent check your systems.
Check your systems for Matsui Securities
Sources
2- note.com5 Nov 2026note.com/deep_poppy8031/n/n4e533a6e457c
- jouhourouei.clipmaster.jp5 Nov 2026jouhourouei.clipmaster.jp/cases
Confidence 80% that this is real and correctly placed. Locations are city centroids at best. Spotted an error? Report a correction.