The post on Spears' Twitpic account said: "Britney has passed today. It is a sad day for everyone. More news to come."
Similar posts were uploaded onto the accounts of DeGeneres and Diddy.
Once the hacking was discovered on Sunday, the false posts were removed and Twitpic shut down part of its service.
Twitpic, which lets users share photos on , but is not owned by Twitter, said it was "implementing a fix [to the problem] immediately".