Equifax reported the breach–likely to be one of the most devastating in history–in a statement late Thursday, explaining that cyber criminals exploited a U.S. website application vulnerability and gained unauthorized access to personally identifiable information, including Social Security numbers, on potentially millions of Americans.
The information was exposed to hackers for more than a month before Equifax detected the breach on July 29.
The credit reporting firm, one of the largest in the United States, has come under increased scrutiny following the disclosure. Bloomberg reported that three senior Equifax executives sold stock in the company worth nearly $1.8 million after the breach was discovered. The company’s stock has been plummeting since Thursday.