plone.protect error while adding an annotation to the document in the viewer

This error is only visible when running your instance in foreground. And after typing c into the pdb it works. (Plone 5)

```
2015-11-21 02:17:14 ERROR plone.protect Error checking for CSRF. Transaction will be aborted since the request is now unsafe:
Traceback (most recent call last):
File "/home/pab/.buildout/eggs/plone.protect-3.0.9-py2.7.egg/plone/protect/auto.py", line 148, in check
return self._check()
File "/home/pab/.buildout/eggs/plone.protect-3.0.9-py2.7.egg/plone/protect/auto.py", line 170, in _check
check(self.request, manager=self.key_manager)
File "/home/pab/.buildout/eggs/plone.protect-3.0.9-py2.7.egg/plone/protect/authenticator.py", line 113, in check
raise Forbidden('Form authenticator is invalid.')
Forbidden: Form authenticator is invalid.
```