Customer support service Zendesk revealed on Thursday, Feb 21, that it had been hacked and three of its clients were affected. Twitter, Tumblr and Pinterest appear to be the three, as they have all contacted users to warn that they may have been affected by the breach, The Next Web reports.

Zendesk noted in a blog post that a hacker had managed to gain access to support information. The company has since patched the vulnerability, but it suspects that the intruder downloaded email addresses and subject lines of users seeking support from three of its customers.

Twitter’s official @Support account subsequently tweeted that the company was “emailing a small percentage of Twitter users who may have been affected by Zendesk’s breach,” adding that no passwords had been involved.

February has been a sad month for cybersecurity. Apple, Facebook and Twitter have all faced embarrassing intrusions recently. Meanwhile, numerous companies, including the New York Times and Wall Street Journal, have come forward to reveal that they have been the victims of hacking attempts believed to originate from hackers connected to the Chinese military.

Recent incidents have caused the U.S. government to take action to help corporations improve their security while also introducing stricter penalties against cybercrimes, TNW says.