https://arstechnica.com/information-technology/2017/10/a-series-of-delays-and-major-errors-led-to-massive-equifax-breach/

A series of costly delays and crucial errors caused Equifax to remain unprotected for months against one of the most severe Web application vulnerabilities in years, the former CEO for the credit reporting service said in written testimony investigating the massive breach that exposed sensitive data for as many as 143 million US Consumers.