Tumblr reported on Thursday that a third party had gained access to the email addresses and passwords of some users.
According to the company, the data is from early 2013 and prior, before Tumblr was acquired by Yahoo. Furthermore, the exposed passwords were not stored in clear text — Tumblr said they were salted and hashed.
Tumblr hasn’t found any evidence that the exposed information was used to access accounts. However, as a precaution, the passwords of the affected users will be reset.
“We recently learned that a third party had obtained access to a set of Tumblr user email addresses with salted and hashed passwords from early 2013, prior to the acquisition of Tumblr by Yahoo,” Tumblr said. “As soon as we became aware of this, our security team thoroughly investigated the matter. Our analysis gives us no reason to believe that this information was used to access Tumblr accounts. As a precaution, however, we will be requiring affected Tumblr users to set a new password.”
Several users reported on Twitter that they have been instructed to change their Tumblr password when trying to log in to their account.
One possible scenario is that hackers accessed a server that was kept online, but no longer maintained by the microblogging platform. Contacted by SecurityWeek, Tumblr said it cannot share additional details as it would provide too much visibility into its investigatory methods.
The company has advised users to visit its Account Security page to learn more about protecting their accounts against unauthorized access. It’s worth noting that Tumblr offers two-factor authentication (2FA), which prevents accounts from being hacked even if the login credentials are compromised.
*Updated with information from Tumblr
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