Home Depot has yet to confirm the estimated number of customer credit and debit card accounts that were compromised during the data breach that affected thousands of stores for five months, and it’s not known whether much of the stolen card info will ever be sold by the hackers now that everyone knows about the massive theft. Regardless, JPMorgan Chase has already begun the process of replacing some cards for customers who may have been affected.

According to Reuters, the bank has confirmed it has sent out an unspecified number of notices to cardholders to let them know that replacement cards are on the way, in some cases as soon as Sept. 30.

The notices tell the customers that their accounts may be “at risk,” but that they can continue to use their current card until a new one arrives; just keep an eye out for odd transactions.

It also reminds cardholders that they will not be liable for unauthorized transactions that are reported promptly to the bank.

Meanwhile, the Wall Street Journal reports that both Visa and MasterCard have sent alerts to thousands of card-issuing banks, asking them to keep their eyes open for potentially fraudulent transactions. The alerts apparently don’t mention Home Depot by name, but it’s obviously a response to the breach that came only five months after a similar attack on Target’s in-store payment system, and which will likely be several times larger, in terms of the number of affected consumers.

Home Depot has had to explain why it failed to learn from the Target hack. The retailer recently explained that it did develop a plan to update its system to prevent this sort of breach, but only about one-fourth of the company’s 2,200 stores had been upgraded by the time the hack was discovered in early September.

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