Tumblr, along with Twitter and Pinterest, was affected by a hack on a third-party customer service tool company, Zendesk. Attackers accessed some user e-mails and subject lines to customer service representatives at the three companies.

Tumblr, Pinterest and Twitter were all affected by a data breach at Zendesk, a company that provides customer service tools to sites around the Web, according to a report from Wired.

Zendesk disclosed the intrusion in a blog post Thursday night, saying that three of its customers had been affected. Wired was the first to report that the customer service files from the three popular Web sites were targeted.

Zendesk said that it believes hackers have downloaded the e-mail addresses and subject lines of messages sent to customer service e-mails at the three companies. No other customers — or their users — were affected, according to the post written by Zendesk chief executive Mikkel Svane.

Wired posted messages from Twitter, Tumblr and Pinterest sent to users who may have been affected by the hack. Anyone who’s contacted the customer service departments at these companies should look through those messages to see if they’ve disclosed contact information. If so, users should be on the lookout for spam e-mails, texts and mailings. Tumblr said specifically that users should review information in messages sent to its support, abuse, legal, law enforcement and general inquiries addresses.

Users should also remember that companies, as a rule, don’t ask for users’ password information over e-mail, so feel free to ignore any suspicious mailings you may get asking for those log-in credentials, even if they look like they legitimately came from Pinterest, Tumblr or Twitter.

Social media users should also keep a close eye on their accounts to make sure that no one has managed to crack their passwords and use those accounts to spread malware.

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