Photos which does not belong to me are appearing in my Dropbox

Photos which does not belong to me, are appearing in my Dropbox since 26 April, taking up my space, and disturbing my use. These photos contains a large portion of pornographic materials. I feel harassed.
I changed my password and deleted the pornographies but new ones are appearing.

改左pw都唔得咁奇怪?

去 Settings -> Security 望望吧, 有 sessions, devices. apps linked 名单.