And firm estimates there are more than 1.9 billion on there
Firm releases report following internal investigation of the incident
Some vendors have patched it, but some haven't.
Ex-CEO Mayer says the firm 'doesn't understand how the act was perpetrated'
Hackers threaten to dump terabytes of customer data
But US firm says no financial information has been accessed
Equifax facing multiple investigations
Leak comes after employee told hackers to 'f*ck off'