Redmine with Amazon S3 didn't work for image

[Jianbo Su]

Hi, 

   I have a redmine with redmine s3 plugin (http://github.com/ka8725/redmine_s3.git)  install on appfog with ruby193 runtime.

   And the redmine S3 plugin works fine with other file types except images. And the log has the following message:

   WARNING: Can't verify CSRF token authenticity. 

  Current user: anonymous

   

   I did log in. How can I fix it?

   Thanks.