What it does?
Subir is a plugin that completely replaces the native attachment uploader with a modern fancy one. It supports multi-upload, frontend validation, drag and drop, on-screen state changes using AJAX.

Status:
Currently its under development.
The partially developed plugin is applied to this site and having effect to New Thread and New Reply currently.

Keep an eye on this thread for further development updates.

Waiting for this!

Waiting for the latest changes in attachment system which is gonna come alongwith 1.8.23
After the release of the same planning to rework on this plugin again.

The development of this plugin is on hold as I have done a PR for the features to be implemented in MyBB core. 
https://github.com/mybb/mybb/pull/4195

If the PR gets merged in MyBB (which likely is going to be with version 1.8.24) the development of this plugin will be officially terminated.

The feature of the PR is already implemented in this site for testing purpose, if anyone is interested about what and how its going to be ...

Thanks.

This is now a core feature of MyBB 
https://github.com/mybb/mybb/pull/4195

No further need of a plugin. Goodbye Subir. Give me back the time I spent on you