HedgeDoc is missing state parameter in OAuth2 flows could lead to CSRF

HedgeDoc is an open source, real-time, collaborative, markdown notes application. Prior to 1.10.4, some of HedgeDoc's OAuth2 endpoints for social login providers such as Google, GitHub, GitLab, Facebook or Dropbox lack CSRF protection, since they don't send a state parameter and verify the response using this parameter. This vulnerability is fixed in 1.10.4.