https://motherboard.vice.com/en_us/article/ne3bv7/equifax-breach-social-security-numbers-researcher-warning

Months before its catastrophic data breach, a security researcher warned Equifax that it was vulnerable to the kind of attack that later compromised the personal data of more than 145 million Americans, Motherboard has learned. Six months after the researcher first notified the company about the vulnerability, Equifax patched it—but only after the massive breach that made headlines had already taken place, according to Equifax's own timeline.

This revelation opens the possibility that more than one group of hackers broke into the company. And, more importantly, it raises new questions about Equifax's own security practices, and whether the company took the right precautions and heeded warnings of serious vulnerabilities before its disastrous hack.