Muji breach: up to 27.26 million customer records and 1.09 million full MUJI Card numbers may have leaked
MUJI app, Muji online store and MUJI Card data (Ryohin Keikaku)
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Ryohin Keikaku, the company behind Muji, says unauthorized access to its systems on Oct 29 2026 may have exposed up to about 27.26 million MUJI app and Muji online store customer records (email addresses, birth dates, gender and member IDs, including former members), about 520,000 of them with names, addresses and phone numbers. Its Nov 4 follow-up adds about 1.09 million MUJI Card records holding full card numbers, birth dates and MUJI Card IDs, which the company had kept from a pre-2021 points scheme; about 345,000 of those cards are still valid. Cardholder names, expiry dates and security codes were not included. Card issuer Credit Saison has seen no rise in fraud, is monitoring the cards and reissues them on request. Ryohin Keikaku says it blocked the access and has found no sign of the data on the dark web so far.
Why this severity: Up to 27.26 million customer records plus about 345,000 valid full credit card numbers with birth dates; the intrusion method has not been disclosed
- Started
- Oct 29, 2026
Affected
Not published yet
Fixed in
No fixed release yet
Timeline3
Second report widens the breach: the 27.26 million records also cover Muji online store members and include member IDs, about 520,000 of them with names, addresses and phone numbers. About 1.09 million MUJI Card records with full card numbers, MUJI Card IDs and birth dates (about 345,000 cards still valid) were also accessible, plus about 120 saved cards (first 6 and last 2 digits and cardholder name). Credit Saison is monitoring for fraud and reissues cards on request.
Ryohin Keikaku discloses that up to about 27.26 million MUJI app customer records (email addresses, birth dates and gender, including former members) may have leaked. It says it blocked the access and applied a fix, and that card data, names, addresses and phone numbers were not involved.
A third party gains unauthorized access to Ryohin Keikaku's (Muji's) systems at about 1:00 a.m. Japan time, according to MUJI Card issuer Credit Saison.
Advisories3
News & write-ups2
Notes & caveats
Only MUJI Cards issued between October 2000 and July 2021 are in the card set; cards issued from August 2021 are not affected. Ryohin Keikaku and Credit Saison are contacting affected customers by email or post. The investigation into the cause and scope is ongoing.
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