Target confirmed this week that hackers who breached its system last year used "credentials they stole" from a vendor of the retail store, according to Reuters.  

"The ongoing forensic investigation has indicated that the intruder stole a vendor's credentials, which were used to access our system," Target spokeswoman Molly Snyder said in a statement.

Snyder failed to say what type of credentials were taken from that vendor.

The Justice Department is still investigating the hacking however, according to Attorney General Eric Holder.

Holder said while testifying at a U.S. Senate hearing that the department isn't just looking for those responsible for the breach but also "any individuals and groups who exploit that data via credit card fraud," according to Reuters.

Approximately 70 million customers had information like addresses, phone numbers, credit and debit card numbers stolen from Black Friday through December 15, according to a company press release.

Holder said the department is taking the breach very seriously.

"While we generally do not discuss specific matters under investigation, I can confirm the department is investigating the breach involving the U.S. retailer, Target," Holder said, according to Reuters.

Target said it is going to try contacting every affected customer.

For those who shopped at Target during the holidays, tips can be found here on Target's website.

"I know that it is frustrating for our guests to learn that this information was taken and we are truly sorry they are having to endure this," said Gregg Steinhafel, chairman, president and chief executive officer, Target, said in a statement earlier this month. 

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