The fallout from Target’s data breach continues to rock the company.

Target announced today that CEO Gregg Steinhafel is resigning, following a huge data breach last year that exposed the credit and debit card information of 40 million retail customers. A 35-year Target veteran, Steinhafel is also stepping down from his role as president and chairman of the company’s board.

“The last several months have tested Target in unprecedented ways,” Steinhafel wrote in a letter to the board today. “From the beginning, I have been committed to ensuring Target emerges from the data breach a better company, more focused on delivering for our guests.”

In January, Target revealed that the data breach also revealed personal information of up to 70 million customers. The breach also revealed Target’s weak security practices, which included storing 3-digit CVV codes from credit cards (which goes against PCI compliance rules). Hackers also stole encrypted debit card PIN data during the attack, though they didn’t have the keys necessary to decrypt the PIN data.

Following the breach, Target said it’s speeding up the adoption of chip-based credit and debit cards. The company is expected to replace its own branded cards with chip and PIN security next year.

Target chief financial officer John Mulligan will serve as interim president and CEO until the company finds a replacement for Steinhafel. The company last week hired a new CIO, Bob DeRodes, replacing the former CIO who resigned in March.