All I find is nodebb-plugin-write-api which is not enough. It doesn't even have login API.I am not familiar with nodejs.And it is not necessary to handle the problems only existing on browser like CSRF.
@SimonQ I am not using the last version of this plugin (I made a fork when the regex issue arised) so I could not reproduce your problem. So I just tried on a testing version of the forum I am in charge and I observe the same behaviour. So it is not just you. I suppose it is a question of tweaking the css though. I will try to have look but I am VERY far to be an expert.