I put the installed problem plugin as Dashboard, but it is actually Defender, as Defender was uninstalled before I got locked out of my site.
Okay, I backed up my databases via VaultPress, and I installed Defender and followed the security scan suggestions. (After the install there were several database line errors reading at the top of my site, these are now gone.) I noticed first, that it damaged database files on my SMF forums. Members cannot register, and certain mods/plugins cannot be altered or accessed, even to uninstall them (on the forums).
So, I went to uninstall Defender, and restore my databases via VaultPress. I was logged out after the backup restore, and now my WordPress login link redirects to my SMF forums login page. So, I am locked out of my site, on top of all the other damage this plugin has caused. Contacted my host, they do not have a database backup prior to the Defender install. (Am working with VaultPress presently.)
Can't get in my site, WordPress is damaged, and so are my SMF forums. On top of this, none of my site members can log in either, nor can new members register.
This is an emergency situation this new Defender plugin caused, and I need some serious help fixing these issues ASAP. Thanks.