A huge collection of exposed login credentials totalling 87GB was recently discovered in file hosting service, Mega.nz. The database, known as Collection #1 is a compilation of more than 2,000 breaches and contains around 773 million unique email addresses and 21 million unique passwords. While majority of the exposed credentials are at least two years old, the database can still be used for credentials stuffing attacks to take over accounts that reuse login credentials across multiple sites. Collection #1 is a subset of exposed data currently available for sale in hacker forums. The seller, who hosted up to five collections in Mega.nz, is peddling some 4TB of leaked credentials.

References:
[1] The 773 Million Record "Collection #1" Data Breach
[2] 773M Password ‘Megabreach’ is Years Old