65.5M accounts from tumblr (tumblr.com) were exposed in this breach. Besides email addresses, it included passwords, which makes it a high-risk breach.
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Email addressesPasswords
In early 2013, tumblr suffered a data breach which resulted in the exposure of over 65 million accounts. The data was later put up for sale on a dark market website and included email addresses and passwords stored as salted SHA1 hashes.
Source: Have I Been Pwned (CC BY 4.0)