Gratipay: Unauthorized access to the slack channel via inside.gratipay.com/appendices/chat

Summary It is possible to force send invites for gratipay slack channel to arbitary email ids with no bruteforce limit. This is done by modifying the coc parameter to 1 in the POST data sent from https://inside.gratipay.com/appendices/chat Description Sending a post request with coc parameter set...