Grork

This plugin will allow you to connect your <code>WordPress blog</code> with your <code>MyBB forum</code>.
When someone registers in MyBB, his information like the username will be stored in WordPress, so when he logins in the blog, he will be automatically logged in in the forum.
The system is tested with MyBB v1.8.*
Download the MyBB-side: https://www.dropbox.com/s/k2llnw3pz1keaz8/MyPress-MyBB.zip?dl=0

MyPress

Connect WordPress with MyBB. Everytime a user registers in your MyBB Forum, he will also be registered in WordPress.

iampsp.com

<ul>
<li>After Login user in WordPress System User Add to Mybb System automatically</li>
</ul>
This is simple plugin. 
If you need a plugin or custom theme, I am at your service through the following communication methods : (non-free) 
Telegram : @MostafaShiraali 
Discord : MostafaShiraali#7754

mybbSync

This Plugin Sync Wordpress User With Mybb.

MyPress vs mybbSync