MyBB Community Forums

* Detailed description of your problem, including steps to reproduce if necessary I went to y forums a day after I installed it and it was hacked because one of the plugins I had installed was exploitable which I didn't know, anyways now whenever I try to remove that plugin/add a new one (http://hackfacility.com/admin/index.php?...ig/plugins) it gives me a 404 error.
* URL to your forum/URL to specific problematic page
http://hackfacility.com/admin/index.php?...ig/plugins
* New installation or upgrade (from which version of MyBB)?
New
* Test user account (if a posting/UserCP issue)
None
* Screenshot or error text, verbatim
403 Forbidden

BTW This is a white hat forum. So don't be like "You're a pineapple you stupid hacker" as I have no intentions to hack people in evil thoughts.

Read:

Error Message: Forbidden
You don't have permission to access /admin/index.php on this server.
Information: This is nearly always a problem with mod_security. mod_security is an extension to Apache that is used for security. In MyBB 1.4, mod_security treats the way the URLs are set out in the ACP as a security threat, so it will deny you access. For information on how to prevent this, see the Wiki page for mod_security. If nothing here works, contact your host provider and ask them to whitelist your domain or hosting account against mod_security - basically so that it doesn't affect you anymore. 

Or read more at: Common Error Messages #Other Error Message
Here at bottom and more...
Wiki - Mod security
Hope that's Help you