Pinterest users began reporting on Thursday night that their accounts had been hacked into and were being used to post weight loss spam – and pictures of butts too.

The makers of the so-called visual discovery tool were alerted to incidents of spam early on Thursday evening, a Pinterest spokesperson told in an emailed statement.

“We began working on cleaning up and placing the accounts in safe mode immediately,” according to the statement. “The accounts have since been secured. As a precaution, Pinners should use unique and strong passwords, and can get more information in our Help Center.”

Pinterest puts accounts with suspicious activity into safe mode so that no changes can be made. Users must reset their passwords in order to unlock their accounts.