Apparel group And ST HD said customer data on roughly 2.5 million people may have been leaked outside the company after a server used for internal work was accessed without authorization.
The company disclosed the possible breach but gave no account of how the access happened, when it was detected, or what kind of information was involved.
The disclosure came on the same day that Mos Burger reported the leak of prepaid card information on about 570,000 cards that had already circulated, and that GMO reported unauthorized access to servers handling its FX trading, with customers also reporting unauthorized transactions on their accounts.
A run of disclosures
Three companies reporting breaches on one day points to neglect across corporate Japan rather than a stretch of bad luck. Each case involves servers holding customer data or payment functions, the kind of system that should be segmented and monitored.
For customers of And ST HD, the company has not said what data may have been taken, which leaves them unable to judge whether passwords, card details or addresses are exposed.